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	$240.64	4.113%	$250.5375	$250.54	$250.55	$250.50
Purchase #2	$82.36	4.562%	$86.1173	$86.12	$86.10	$86.10
Purchase #3	$81.42	3.116%	$83.957	$83.96	$83.95	$84.00
Purchase #4	$22.52	4.423%	$23.5161	$23.52	$23.50	$23.50
Purchase #5	$87.87	7.588%	$94.5376	$94.54	$94.55	$94.50
Purchase #6	$21.49	4.815%	$22.5247	$22.52	$22.50	$22.50
Purchase #7	$165.89	11.631%	$185.1847	$185.18	$185.20	$185.20
7 purchase totals =	$702.19		$746.3749	$746.38	$746.35	$746.30