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	$91.46	5.862%	$96.8214	$96.82	$96.80	$96.80
Purchase #2	$97.31	8.238%	$105.3264	$105.33	$105.35	$105.30
Purchase #3	$154.75	7.482%	$166.3284	$166.33	$166.35	$166.30
Purchase #4	$165.37	12.439%	$185.9404	$185.94	$185.95	$185.90
Purchase #5	$29.64	8.234%	$32.0806	$32.08	$32.10	$32.10
Purchase #6	$61.98	4.717%	$64.9036	$64.90	$64.90	$64.90
Purchase #7	$178.55	3.141%	$184.1583	$184.16	$184.15	$184.20
7 purchase totals =	$779.06		$835.5591	$835.56	$835.60	$835.50