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	$191.78	4.765%	$200.9183	$200.92	$200.90	$200.90
Purchase #2	$245.98	9.518%	$269.3924	$269.39	$269.40	$269.40
Purchase #3	$91.83	4.201%	$95.6878	$95.69	$95.70	$95.70
Purchase #4	$20.99	5.142%	$22.0693	$22.07	$22.05	$22.10
Purchase #5	$229.82	3.248%	$237.2846	$237.28	$237.30	$237.30
Purchase #6	$181.72	4.114%	$189.196	$189.20	$189.20	$189.20
Purchase #7	$69.59	12.621%	$78.373	$78.37	$78.35	$78.40
7 purchase totals =	$1,031.71		$1,092.9214	$1,092.92	$1,092.90	$1,093.00