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	$223.38	9.553%	$244.7195	$244.72	$244.70	$244.70
Purchase #2	$33.36	5.668%	$35.2508	$35.25	$35.25	$35.30
Purchase #3	$197.64	12.578%	$222.4992	$222.50	$222.50	$222.50
Purchase #4	$70.68	11.265%	$78.6421	$78.64	$78.65	$78.60
Purchase #5	$148.50	13.390%	$168.3842	$168.38	$168.40	$168.40
Purchase #6	$52.37	3.695%	$54.3051	$54.31	$54.30	$54.30
Purchase #7	$50.99	7.344%	$54.7347	$54.73	$54.75	$54.70
7 purchase totals =	$776.92		$858.5356	$858.53	$858.55	$858.50