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	$57.88	11.842%	$64.7341	$64.73	$64.75	$64.70
Purchase #2	$168.28	10.168%	$185.3907	$185.39	$185.40	$185.40
Purchase #3	$37.78	13.791%	$42.9902	$42.99	$43.00	$43.00
Purchase #4	$195.97	4.739%	$205.257	$205.26	$205.25	$205.30
Purchase #5	$15.61	3.260%	$16.1189	$16.12	$16.10	$16.10
Purchase #6	$90.35	10.485%	$99.8232	$99.82	$99.80	$99.80
Purchase #7	$223.96	4.627%	$234.3226	$234.32	$234.30	$234.30
7 purchase totals =	$789.83		$848.6367	$848.63	$848.60	$848.60