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	$186.92	5.209%	$196.6567	$196.66	$196.65	$196.70
Purchase #2	$130.68	8.384%	$141.6362	$141.64	$141.65	$141.60
Purchase #3	$11.62	5.814%	$12.2956	$12.30	$12.30	$12.30
Purchase #4	$31.71	6.655%	$33.8203	$33.82	$33.80	$33.80
Purchase #5	$155.41	6.388%	$165.3376	$165.34	$165.35	$165.30
Purchase #6	$148.63	7.346%	$159.5484	$159.55	$159.55	$159.50
Purchase #7	$164.46	5.681%	$173.803	$173.80	$173.80	$173.80
7 purchase totals =	$829.43		$883.0978	$883.11	$883.10	$883.00