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	$72.70	7.475%	$78.1343	$78.13	$78.15	$78.10
Purchase #2	$146.96	5.718%	$155.3632	$155.36	$155.35	$155.40
Purchase #3	$230.86	5.192%	$242.8463	$242.85	$242.85	$242.80
Purchase #4	$190.58	12.152%	$213.7393	$213.74	$213.75	$213.70
Purchase #5	$179.26	6.560%	$191.0195	$191.02	$191.00	$191.00
Purchase #6	$146.86	3.476%	$151.9649	$151.96	$151.95	$152.00
Purchase #7	$240.62	11.489%	$268.2648	$268.26	$268.25	$268.30
7 purchase totals =	$1,207.84		$1,301.3323	$1,301.32	$1,301.30	$1,301.30