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	$81.43	12.695%	$91.7675	$91.77	$91.75	$91.80
Purchase #2	$202.50	3.434%	$209.4539	$209.45	$209.45	$209.50
Purchase #3	$96.77	7.613%	$104.1371	$104.14	$104.15	$104.10
Purchase #4	$37.49	13.768%	$42.6516	$42.65	$42.65	$42.70
Purchase #5	$247.65	4.304%	$258.3089	$258.31	$258.30	$258.30
Purchase #6	$246.37	10.119%	$271.3002	$271.30	$271.30	$271.30
Purchase #7	$165.63	9.441%	$181.2671	$181.27	$181.25	$181.30
7 purchase totals =	$1,077.84		$1,158.8863	$1,158.89	$1,158.85	$1,159.00