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	$243.41	10.679%	$269.4038	$269.40	$269.40	$269.40
Purchase #2	$104.98	3.220%	$108.3604	$108.36	$108.35	$108.40
Purchase #3	$150.85	13.680%	$171.4863	$171.49	$171.50	$171.50
Purchase #4	$193.40	9.510%	$211.7923	$211.79	$211.80	$211.80
Purchase #5	$82.43	10.253%	$90.8815	$90.88	$90.90	$90.90
Purchase #6	$224.44	8.478%	$243.468	$243.47	$243.45	$243.50
Purchase #7	$55.61	3.650%	$57.6398	$57.64	$57.65	$57.60
7 purchase totals =	$1,055.12		$1,153.0321	$1,153.03	$1,153.05	$1,153.10