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	$184.82	8.226%	$200.0233	$200.02	$200.00	$200.00
Purchase #2	$86.83	7.170%	$93.0557	$93.06	$93.05	$93.10
Purchase #3	$73.42	8.872%	$79.9338	$79.93	$79.95	$79.90
Purchase #4	$105.44	7.240%	$113.0739	$113.07	$113.05	$113.10
Purchase #5	$72.86	10.574%	$80.5642	$80.56	$80.55	$80.60
Purchase #6	$197.78	12.553%	$222.6073	$222.61	$222.60	$222.60
Purchase #7	$205.76	11.520%	$229.4636	$229.46	$229.45	$229.50
7 purchase totals =	$926.91		$1,018.7218	$1,018.71	$1,018.65	$1,018.80