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	$201.43	10.819%	$223.2227	$223.22	$223.20	$223.20
Purchase #2	$159.41	9.322%	$174.2702	$174.27	$174.25	$174.30
Purchase #3	$150.43	4.525%	$157.237	$157.24	$157.25	$157.20
Purchase #4	$123.25	4.481%	$128.7728	$128.77	$128.75	$128.80
Purchase #5	$168.94	11.787%	$188.853	$188.85	$188.85	$188.90
Purchase #6	$111.98	9.864%	$123.0257	$123.03	$123.05	$123.00
Purchase #7	$152.29	4.365%	$158.9375	$158.94	$158.95	$158.90
7 purchase totals =	$1,067.73		$1,154.3189	$1,154.32	$1,154.30	$1,154.30