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	$47.52	11.754%	$53.1055	$53.11	$53.10	$53.10
Purchase #2	$151.53	11.201%	$168.5029	$168.50	$168.50	$168.50
Purchase #3	$74.65	3.789%	$77.4785	$77.48	$77.50	$77.50
Purchase #4	$85.64	10.696%	$94.8001	$94.80	$94.80	$94.80
Purchase #5	$122.41	13.646%	$139.1141	$139.11	$139.10	$139.10
Purchase #6	$237.64	3.123%	$245.0615	$245.06	$245.05	$245.10
Purchase #7	$10.40	10.812%	$11.5244	$11.52	$11.50	$11.50
7 purchase totals =	$729.79		$789.5870	$789.58	$789.55	$789.60