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	$243.88	4.626%	$255.1619	$255.16	$255.15	$255.20
Purchase #2	$240.67	11.386%	$268.0727	$268.07	$268.05	$268.10
Purchase #3	$98.50	12.368%	$110.6825	$110.68	$110.70	$110.70
Purchase #4	$172.75	12.606%	$194.5269	$194.53	$194.55	$194.50
Purchase #5	$92.27	12.112%	$103.4457	$103.45	$103.45	$103.40
Purchase #6	$63.46	4.228%	$66.1431	$66.14	$66.15	$66.10
Purchase #7	$25.74	10.459%	$28.4321	$28.43	$28.45	$28.40
7 purchase totals =	$937.27		$1,026.4649	$1,026.46	$1,026.50	$1,026.40