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	$147.73	3.643%	$153.1118	$153.11	$153.10	$153.10
Purchase #2	$78.43	5.823%	$82.997	$83.00	$83.00	$83.00
Purchase #3	$58.89	9.224%	$64.322	$64.32	$64.30	$64.30
Purchase #4	$183.45	4.629%	$191.9419	$191.94	$191.95	$191.90
Purchase #5	$59.84	3.630%	$62.0122	$62.01	$62.00	$62.00
Purchase #6	$25.83	11.862%	$28.894	$28.89	$28.90	$28.90
Purchase #7	$161.56	4.152%	$168.268	$168.27	$168.25	$168.30
7 purchase totals =	$715.73		$751.5469	$751.54	$751.50	$751.50