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	$198.94	10.244%	$219.3194	$219.32	$219.30	$219.30
Purchase #2	$70.44	12.836%	$79.4817	$79.48	$79.50	$79.50
Purchase #3	$55.72	7.558%	$59.9313	$59.93	$59.95	$59.90
Purchase #4	$238.75	13.773%	$271.633	$271.63	$271.65	$271.60
Purchase #5	$223.53	13.800%	$254.3771	$254.38	$254.40	$254.40
Purchase #6	$28.30	3.401%	$29.2625	$29.26	$29.25	$29.30
Purchase #7	$114.82	12.236%	$128.8694	$128.87	$128.85	$128.90
7 purchase totals =	$930.50		$1,042.8744	$1,042.87	$1,042.90	$1,042.90