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	$191.72	4.361%	$200.0809	$200.08	$200.10	$200.10
Purchase #2	$98.64	3.862%	$102.4495	$102.45	$102.45	$102.40
Purchase #3	$221.44	4.208%	$230.7582	$230.76	$230.75	$230.80
Purchase #4	$74.31	12.267%	$83.4256	$83.43	$83.45	$83.40
Purchase #5	$233.79	13.153%	$264.5404	$264.54	$264.55	$264.50
Purchase #6	$79.76	13.430%	$90.4718	$90.47	$90.45	$90.50
Purchase #7	$204.33	7.133%	$218.9049	$218.90	$218.90	$218.90
7 purchase totals =	$1,103.99		$1,190.6313	$1,190.63	$1,190.65	$1,190.60