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	$147.26	10.226%	$162.3188	$162.32	$162.30	$162.30
Purchase #2	$249.96	5.580%	$263.9078	$263.91	$263.90	$263.90
Purchase #3	$106.46	5.308%	$112.1109	$112.11	$112.10	$112.10
Purchase #4	$71.96	7.468%	$77.334	$77.33	$77.35	$77.30
Purchase #5	$234.70	7.204%	$251.6078	$251.61	$251.60	$251.60
Purchase #6	$51.55	3.634%	$53.4233	$53.42	$53.40	$53.40
Purchase #7	$133.76	11.287%	$148.8575	$148.86	$148.85	$148.90
7 purchase totals =	$995.65		$1,069.5601	$1,069.56	$1,069.50	$1,069.50