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	$186.95	9.252%	$204.2466	$204.25	$204.25	$204.20
Purchase #2	$61.80	12.418%	$69.4743	$69.47	$69.45	$69.50
Purchase #3	$56.56	5.264%	$59.5373	$59.54	$59.55	$59.50
Purchase #4	$195.32	13.401%	$221.4948	$221.49	$221.50	$221.50
Purchase #5	$48.75	4.330%	$50.8609	$50.86	$50.85	$50.90
Purchase #6	$156.44	9.483%	$171.2752	$171.28	$171.30	$171.30
Purchase #7	$216.44	6.511%	$230.5324	$230.53	$230.55	$230.50
7 purchase totals =	$922.26		$1,007.4215	$1,007.42	$1,007.45	$1,007.40