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	$43.72	4.213%	$45.5619	$45.56	$45.55	$45.60
Purchase #2	$185.83	12.608%	$209.2594	$209.26	$209.25	$209.30
Purchase #3	$51.72	11.135%	$57.479	$57.48	$57.50	$57.50
Purchase #4	$100.56	3.294%	$103.8724	$103.87	$103.85	$103.90
Purchase #5	$70.92	11.175%	$78.8453	$78.85	$78.85	$78.80
Purchase #6	$99.33	13.118%	$112.3601	$112.36	$112.35	$112.40
Purchase #7	$81.62	10.397%	$90.106	$90.11	$90.10	$90.10
7 purchase totals =	$633.70		$697.4841	$697.49	$697.45	$697.60