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	$225.70	4.735%	$236.3869	$236.39	$236.40	$236.40
Purchase #2	$18.42	12.781%	$20.7743	$20.77	$20.75	$20.80
Purchase #3	$188.82	3.431%	$195.2984	$195.30	$195.30	$195.30
Purchase #4	$47.28	6.728%	$50.461	$50.46	$50.45	$50.50
Purchase #5	$133.96	13.483%	$152.0218	$152.02	$152.00	$152.00
Purchase #6	$90.86	3.328%	$93.8838	$93.88	$93.90	$93.90
Purchase #7	$205.84	11.567%	$229.6495	$229.65	$229.65	$229.60
7 purchase totals =	$910.88		$978.4757	$978.47	$978.45	$978.50