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	$93.73	5.583%	$98.9629	$98.96	$98.95	$99.00
Purchase #2	$140.27	5.767%	$148.3594	$148.36	$148.35	$148.40
Purchase #3	$235.42	4.416%	$245.8161	$245.82	$245.80	$245.80
Purchase #4	$141.56	12.616%	$159.4192	$159.42	$159.40	$159.40
Purchase #5	$29.47	5.401%	$31.0617	$31.06	$31.05	$31.10
Purchase #6	$235.31	3.640%	$243.8753	$243.88	$243.90	$243.90
Purchase #7	$127.61	6.647%	$136.0922	$136.09	$136.10	$136.10
7 purchase totals =	$1,003.37		$1,063.5868	$1,063.59	$1,063.55	$1,063.70