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	$250.40	9.822%	$274.9943	$274.99	$275.00	$275.00
Purchase #2	$9.73	5.556%	$10.2706	$10.27	$10.25	$10.30
Purchase #3	$69.97	11.801%	$78.2272	$78.23	$78.25	$78.20
Purchase #4	$130.55	8.261%	$141.3347	$141.33	$141.35	$141.30
Purchase #5	$185.65	5.658%	$196.1541	$196.15	$196.15	$196.20
Purchase #6	$196.90	5.255%	$207.2471	$207.25	$207.25	$207.20
Purchase #7	$165.87	6.361%	$176.421	$176.42	$176.40	$176.40
7 purchase totals =	$1,009.07		$1,084.6490	$1,084.64	$1,084.65	$1,084.60