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	$70.92	3.714%	$73.554	$73.55	$73.55	$73.60
Purchase #2	$185.49	3.454%	$191.8968	$191.90	$191.90	$191.90
Purchase #3	$101.44	5.211%	$106.726	$106.73	$106.75	$106.70
Purchase #4	$67.62	3.516%	$69.9975	$70.00	$70.00	$70.00
Purchase #5	$66.72	9.634%	$73.1478	$73.15	$73.15	$73.10
Purchase #6	$104.91	7.609%	$112.8926	$112.89	$112.90	$112.90
Purchase #7	$53.45	11.501%	$59.5973	$59.60	$59.60	$59.60
7 purchase totals =	$650.55		$687.8120	$687.82	$687.85	$687.80