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	$168.29	11.173%	$187.093	$187.09	$187.10	$187.10
Purchase #2	$83.46	11.146%	$92.7625	$92.76	$92.75	$92.80
Purchase #3	$205.73	9.775%	$225.8401	$225.84	$225.85	$225.80
Purchase #4	$174.79	9.281%	$191.0123	$191.01	$191.00	$191.00
Purchase #5	$247.25	4.515%	$258.4133	$258.41	$258.40	$258.40
Purchase #6	$48.89	5.415%	$51.5374	$51.54	$51.55	$51.50
Purchase #7	$10.31	11.443%	$11.4898	$11.49	$11.50	$11.50
7 purchase totals =	$938.72		$1,018.1484	$1,018.14	$1,018.15	$1,018.10