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	$48.70	11.538%	$54.319	$54.32	$54.30	$54.30
Purchase #2	$73.29	13.862%	$83.4495	$83.45	$83.45	$83.40
Purchase #3	$62.31	11.410%	$69.4196	$69.42	$69.40	$69.40
Purchase #4	$140.50	4.712%	$147.1204	$147.12	$147.10	$147.10
Purchase #5	$118.58	8.137%	$128.2289	$128.23	$128.25	$128.20
Purchase #6	$211.34	5.673%	$223.3293	$223.33	$223.35	$223.30
Purchase #7	$142.66	4.829%	$149.5491	$149.55	$149.55	$149.50
7 purchase totals =	$797.38		$855.4158	$855.42	$855.40	$855.20