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	$96.56	13.672%	$109.7617	$109.76	$109.75	$109.80
Purchase #2	$230.64	8.730%	$250.7749	$250.77	$250.75	$250.80
Purchase #3	$203.41	9.837%	$223.4194	$223.42	$223.40	$223.40
Purchase #4	$53.53	5.146%	$56.2847	$56.28	$56.30	$56.30
Purchase #5	$45.81	12.407%	$51.4936	$51.49	$51.50	$51.50
Purchase #6	$233.71	9.809%	$256.6346	$256.63	$256.65	$256.60
Purchase #7	$99.59	3.182%	$102.759	$102.76	$102.75	$102.80
7 purchase totals =	$963.25		$1,051.1279	$1,051.11	$1,051.10	$1,051.20