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	$167.91	10.487%	$185.5187	$185.52	$185.50	$185.50
Purchase #2	$92.93	7.723%	$100.107	$100.11	$100.10	$100.10
Purchase #3	$195.42	4.501%	$204.2159	$204.22	$204.20	$204.20
Purchase #4	$186.42	5.185%	$196.0859	$196.09	$196.10	$196.10
Purchase #5	$22.49	4.574%	$23.5187	$23.52	$23.50	$23.50
Purchase #6	$72.98	11.171%	$81.1326	$81.13	$81.15	$81.10
Purchase #7	$51.86	12.402%	$58.2917	$58.29	$58.30	$58.30
7 purchase totals =	$790.01		$848.8705	$848.88	$848.85	$848.80