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	$188.88	4.242%	$196.8923	$196.89	$196.90	$196.90
Purchase #2	$47.47	8.199%	$51.3621	$51.36	$51.35	$51.40
Purchase #3	$172.49	7.778%	$185.9063	$185.91	$185.90	$185.90
Purchase #4	$115.51	8.152%	$124.9264	$124.93	$124.95	$124.90
Purchase #5	$119.61	8.724%	$130.0448	$130.04	$130.05	$130.00
Purchase #6	$97.98	13.268%	$110.98	$110.98	$111.00	$111.00
Purchase #7	$5.78	4.394%	$6.034	$6.03	$6.05	$6.00
7 purchase totals =	$747.72		$806.1459	$806.14	$806.20	$806.10