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	$188.73	3.111%	$194.6014	$194.60	$194.60	$194.60
Purchase #2	$26.51	4.275%	$27.6433	$27.64	$27.65	$27.60
Purchase #3	$197.30	12.725%	$222.4064	$222.41	$222.40	$222.40
Purchase #4	$74.97	12.345%	$84.225	$84.23	$84.25	$84.20
Purchase #5	$196.59	11.133%	$218.4764	$218.48	$218.50	$218.50
Purchase #6	$65.33	9.326%	$71.4227	$71.42	$71.40	$71.40
Purchase #7	$218.51	6.417%	$232.5318	$232.53	$232.55	$232.50
7 purchase totals =	$967.94		$1,051.3070	$1,051.31	$1,051.35	$1,051.20