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	$185.84	4.608%	$194.4035	$194.40	$194.40	$194.40
Purchase #2	$233.54	6.603%	$248.9606	$248.96	$248.95	$249.00
Purchase #3	$88.85	11.813%	$99.3459	$99.35	$99.35	$99.30
Purchase #4	$248.39	12.469%	$279.3617	$279.36	$279.35	$279.40
Purchase #5	$205.86	8.401%	$223.1543	$223.15	$223.15	$223.20
Purchase #6	$17.53	7.741%	$18.887	$18.89	$18.90	$18.90
Purchase #7	$74.83	3.345%	$77.3331	$77.33	$77.35	$77.30
7 purchase totals =	$1,054.84		$1,141.4461	$1,141.44	$1,141.45	$1,141.50