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	$114.73	13.360%	$130.0579	$130.06	$130.05	$130.10
Purchase #2	$90.77	3.454%	$93.9052	$93.91	$93.90	$93.90
Purchase #3	$127.39	7.254%	$136.6309	$136.63	$136.65	$136.60
Purchase #4	$151.96	10.809%	$168.3854	$168.39	$168.40	$168.40
Purchase #5	$102.74	9.277%	$112.2712	$112.27	$112.25	$112.30
Purchase #6	$250.84	11.261%	$279.0871	$279.09	$279.10	$279.10
Purchase #7	$89.36	8.504%	$96.9592	$96.96	$96.95	$97.00
7 purchase totals =	$927.79		$1,017.2969	$1,017.31	$1,017.30	$1,017.40