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	$42.33	7.846%	$45.6512	$45.65	$45.65	$45.70
Purchase #2	$72.65	7.736%	$78.2702	$78.27	$78.25	$78.30
Purchase #3	$117.77	9.853%	$129.3739	$129.37	$129.35	$129.40
Purchase #4	$112.56	5.773%	$119.0581	$119.06	$119.05	$119.10
Purchase #5	$199.70	5.439%	$210.5617	$210.56	$210.55	$210.60
Purchase #6	$98.79	11.740%	$110.3879	$110.39	$110.40	$110.40
Purchase #7	$218.90	9.744%	$240.2296	$240.23	$240.25	$240.20
7 purchase totals =	$862.70		$933.5326	$933.53	$933.50	$933.70