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	$64.39	13.710%	$73.2179	$73.22	$73.20	$73.20
Purchase #2	$79.94	12.759%	$90.1395	$90.14	$90.15	$90.10
Purchase #3	$85.89	5.506%	$90.6191	$90.62	$90.60	$90.60
Purchase #4	$198.29	13.637%	$225.3308	$225.33	$225.35	$225.30
Purchase #5	$204.90	13.654%	$232.877	$232.88	$232.90	$232.90
Purchase #6	$135.36	7.559%	$145.5919	$145.59	$145.60	$145.60
Purchase #7	$166.60	7.421%	$178.9634	$178.96	$178.95	$179.00
7 purchase totals =	$935.37		$1,036.7396	$1,036.74	$1,036.75	$1,036.70