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	$159.36	8.505%	$172.9136	$172.91	$172.90	$172.90
Purchase #2	$69.46	13.435%	$78.792	$78.79	$78.80	$78.80
Purchase #3	$71.57	5.583%	$75.5658	$75.57	$75.55	$75.60
Purchase #4	$166.47	12.125%	$186.6545	$186.65	$186.65	$186.70
Purchase #5	$237.52	4.818%	$248.9637	$248.96	$248.95	$249.00
Purchase #6	$174.74	4.749%	$183.0384	$183.04	$183.05	$183.00
Purchase #7	$81.89	10.399%	$90.4057	$90.41	$90.40	$90.40
7 purchase totals =	$961.01		$1,036.3337	$1,036.33	$1,036.30	$1,036.40