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	$82.94	6.299%	$88.1644	$88.16	$88.15	$88.20
Purchase #2	$80.42	7.567%	$86.5054	$86.51	$86.50	$86.50
Purchase #3	$86.70	5.252%	$91.2535	$91.25	$91.25	$91.30
Purchase #4	$215.95	9.127%	$235.6598	$235.66	$235.65	$235.70
Purchase #5	$135.26	5.831%	$143.147	$143.15	$143.15	$143.10
Purchase #6	$156.74	6.841%	$167.4626	$167.46	$167.45	$167.50
Purchase #7	$250.88	13.648%	$285.1201	$285.12	$285.10	$285.10
7 purchase totals =	$1,008.89		$1,097.3128	$1,097.31	$1,097.25	$1,097.40