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	$216.85	3.595%	$224.6458	$224.65	$224.65	$224.60
Purchase #2	$47.81	5.545%	$50.4611	$50.46	$50.45	$50.50
Purchase #3	$99.74	9.787%	$109.5016	$109.50	$109.50	$109.50
Purchase #4	$194.32	12.337%	$218.2933	$218.29	$218.30	$218.30
Purchase #5	$241.90	11.227%	$269.0581	$269.06	$269.05	$269.10
Purchase #6	$185.30	3.325%	$191.4612	$191.46	$191.45	$191.50
Purchase #7	$122.64	6.411%	$130.5025	$130.50	$130.50	$130.50
7 purchase totals =	$1,108.56		$1,193.9236	$1,193.92	$1,193.90	$1,194.00