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	$176.36	6.112%	$187.1391	$187.14	$187.15	$187.10
Purchase #2	$96.43	3.227%	$99.5418	$99.54	$99.55	$99.50
Purchase #3	$38.28	7.717%	$41.2341	$41.23	$41.25	$41.20
Purchase #4	$7.45	5.805%	$7.8825	$7.88	$7.90	$7.90
Purchase #5	$47.67	6.441%	$50.7404	$50.74	$50.75	$50.70
Purchase #6	$13.41	12.691%	$15.1119	$15.11	$15.10	$15.10
Purchase #7	$39.26	8.546%	$42.6152	$42.62	$42.60	$42.60
7 purchase totals =	$418.86		$444.2650	$444.26	$444.30	$444.10