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	$113.43	7.571%	$122.0178	$122.02	$122.00	$122.00
Purchase #2	$183.76	4.120%	$191.3309	$191.33	$191.35	$191.30
Purchase #3	$30.89	4.418%	$32.2547	$32.25	$32.25	$32.30
Purchase #4	$148.31	9.219%	$161.9827	$161.98	$162.00	$162.00
Purchase #5	$78.47	6.302%	$83.4152	$83.42	$83.40	$83.40
Purchase #6	$55.50	6.869%	$59.3123	$59.31	$59.30	$59.30
Purchase #7	$188.89	3.406%	$195.3236	$195.32	$195.30	$195.30
7 purchase totals =	$799.25		$845.6372	$845.63	$845.60	$845.60