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	$136.56	7.198%	$146.3896	$146.39	$146.40	$146.40
Purchase #2	$236.70	11.244%	$263.3145	$263.31	$263.30	$263.30
Purchase #3	$154.33	11.158%	$171.5501	$171.55	$171.55	$171.60
Purchase #4	$51.64	4.442%	$53.9338	$53.93	$53.95	$53.90
Purchase #5	$39.94	10.499%	$44.1333	$44.13	$44.15	$44.10
Purchase #6	$122.95	3.356%	$127.0762	$127.08	$127.10	$127.10
Purchase #7	$202.77	6.422%	$215.7919	$215.79	$215.80	$215.80
7 purchase totals =	$944.89		$1,022.1894	$1,022.18	$1,022.25	$1,022.20