Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$137.72	9.401%	$150.6671	$150.67	$150.65	$150.70
Purchase #2	$160.47	3.712%	$166.4266	$166.43	$166.45	$166.40
Purchase #3	$110.27	5.444%	$116.2731	$116.27	$116.25	$116.30
Purchase #4	$180.94	12.479%	$203.5195	$203.52	$203.50	$203.50
Purchase #5	$211.94	10.623%	$234.4544	$234.45	$234.45	$234.50
Purchase #6	$243.38	9.148%	$265.6444	$265.64	$265.65	$265.60
Purchase #7	$232.59	4.443%	$242.924	$242.92	$242.90	$242.90
7 purchase totals =	$1,277.31		$1,379.9091	$1,379.90	$1,379.85	$1,379.90