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	$232.56	3.339%	$240.3252	$240.33	$240.35	$240.30
Purchase #2	$216.71	11.746%	$242.1648	$242.16	$242.15	$242.20
Purchase #3	$149.80	11.854%	$167.5573	$167.56	$167.55	$167.60
Purchase #4	$222.60	13.165%	$251.9053	$251.91	$251.90	$251.90
Purchase #5	$137.89	13.364%	$156.3176	$156.32	$156.30	$156.30
Purchase #6	$187.56	4.244%	$195.52	$195.52	$195.50	$195.50
Purchase #7	$105.28	3.794%	$109.2743	$109.27	$109.25	$109.30
7 purchase totals =	$1,252.40		$1,363.0645	$1,363.07	$1,363.00	$1,363.10