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	$223.34	13.379%	$253.2207	$253.22	$253.20	$253.20
Purchase #2	$119.49	10.549%	$132.095	$132.10	$132.10	$132.10
Purchase #3	$145.65	13.749%	$165.6754	$165.68	$165.70	$165.70
Purchase #4	$98.61	3.364%	$101.9272	$101.93	$101.95	$101.90
Purchase #5	$35.59	13.542%	$40.4096	$40.41	$40.40	$40.40
Purchase #6	$191.39	9.859%	$210.2591	$210.26	$210.25	$210.30
Purchase #7	$165.76	3.485%	$171.5367	$171.54	$171.55	$171.50
7 purchase totals =	$979.83		$1,075.1237	$1,075.14	$1,075.15	$1,075.10