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	$62.27	11.281%	$69.2947	$69.29	$69.30	$69.30
Purchase #2	$147.89	4.500%	$154.5451	$154.55	$154.55	$154.50
Purchase #3	$124.84	13.780%	$142.043	$142.04	$142.05	$142.00
Purchase #4	$47.60	6.668%	$50.774	$50.77	$50.75	$50.80
Purchase #5	$139.64	9.639%	$153.0999	$153.10	$153.10	$153.10
Purchase #6	$247.29	11.407%	$275.4984	$275.50	$275.50	$275.50
Purchase #7	$171.41	10.836%	$189.984	$189.98	$190.00	$190.00
7 purchase totals =	$940.94		$1,035.2391	$1,035.23	$1,035.25	$1,035.20