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	$66.91	13.342%	$75.8371	$75.84	$75.85	$75.80
Purchase #2	$205.51	8.506%	$222.9907	$222.99	$223.00	$223.00
Purchase #3	$233.50	11.267%	$259.8084	$259.81	$259.80	$259.80
Purchase #4	$141.38	7.837%	$152.46	$152.46	$152.45	$152.50
Purchase #5	$27.76	9.703%	$30.4536	$30.45	$30.45	$30.50
Purchase #6	$99.68	9.414%	$109.0639	$109.06	$109.05	$109.10
Purchase #7	$219.77	7.301%	$235.8154	$235.82	$235.80	$235.80
7 purchase totals =	$994.51		$1,086.4291	$1,086.43	$1,086.40	$1,086.50