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	$144.42	4.843%	$151.4143	$151.41	$151.40	$151.40
Purchase #2	$147.66	3.810%	$153.2858	$153.29	$153.30	$153.30
Purchase #3	$85.28	13.856%	$97.0964	$97.10	$97.10	$97.10
Purchase #4	$106.46	7.300%	$114.2316	$114.23	$114.25	$114.20
Purchase #5	$221.38	13.646%	$251.5895	$251.59	$251.60	$251.60
Purchase #6	$156.50	6.808%	$167.1545	$167.15	$167.15	$167.20
Purchase #7	$40.47	3.752%	$41.9884	$41.99	$42.00	$42.00
7 purchase totals =	$902.17		$976.7605	$976.76	$976.80	$976.80