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	$31.27	5.421%	$32.9651	$32.97	$32.95	$33.00
Purchase #2	$46.43	7.813%	$50.0576	$50.06	$50.05	$50.10
Purchase #3	$6.67	11.448%	$7.4336	$7.43	$7.45	$7.40
Purchase #4	$86.71	10.868%	$96.1336	$96.13	$96.15	$96.10
Purchase #5	$45.46	5.543%	$47.9798	$47.98	$48.00	$48.00
Purchase #6	$80.83	5.664%	$85.4082	$85.41	$85.40	$85.40
Purchase #7	$186.28	12.363%	$209.3098	$209.31	$209.30	$209.30
7 purchase totals =	$483.65		$529.2877	$529.29	$529.30	$529.30