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	$95.97	3.274%	$99.1121	$99.11	$99.10	$99.10
Purchase #2	$214.82	7.255%	$230.4052	$230.41	$230.40	$230.40
Purchase #3	$19.89	5.199%	$20.9241	$20.92	$20.90	$20.90
Purchase #4	$27.76	4.872%	$29.1125	$29.11	$29.10	$29.10
Purchase #5	$161.86	3.447%	$167.4393	$167.44	$167.45	$167.40
Purchase #6	$114.26	11.814%	$127.7587	$127.76	$127.75	$127.80
Purchase #7	$56.45	9.581%	$61.8585	$61.86	$61.85	$61.90
7 purchase totals =	$691.01		$736.6104	$736.61	$736.55	$736.60