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	$31.59	12.389%	$35.5037	$35.50	$35.50	$35.50
Purchase #2	$188.88	5.498%	$199.2646	$199.26	$199.25	$199.30
Purchase #3	$47.76	12.141%	$53.5585	$53.56	$53.55	$53.60
Purchase #4	$176.46	10.678%	$195.3024	$195.30	$195.30	$195.30
Purchase #5	$229.34	4.181%	$238.9287	$238.93	$238.95	$238.90
Purchase #6	$222.54	9.469%	$243.6123	$243.61	$243.60	$243.60
Purchase #7	$146.77	10.646%	$162.3951	$162.40	$162.40	$162.40
7 purchase totals =	$1,043.34		$1,128.5653	$1,128.56	$1,128.55	$1,128.60