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	$188.98	5.471%	$199.3191	$199.32	$199.30	$199.30
Purchase #2	$229.50	5.409%	$241.9137	$241.91	$241.90	$241.90
Purchase #3	$62.62	11.335%	$69.718	$69.72	$69.70	$69.70
Purchase #4	$12.25	13.383%	$13.8894	$13.89	$13.90	$13.90
Purchase #5	$103.41	5.468%	$109.0645	$109.06	$109.05	$109.10
Purchase #6	$48.77	8.642%	$52.9847	$52.98	$53.00	$53.00
Purchase #7	$41.31	4.774%	$43.2821	$43.28	$43.30	$43.30
7 purchase totals =	$686.84		$730.1715	$730.16	$730.15	$730.20