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	$135.77	8.681%	$147.5562	$147.56	$147.55	$147.60
Purchase #2	$106.89	4.650%	$111.8604	$111.86	$111.85	$111.90
Purchase #3	$9.75	12.532%	$10.9719	$10.97	$10.95	$11.00
Purchase #4	$202.26	3.630%	$209.602	$209.60	$209.60	$209.60
Purchase #5	$115.34	3.442%	$119.31	$119.31	$119.30	$119.30
Purchase #6	$56.33	5.754%	$59.5712	$59.57	$59.55	$59.60
Purchase #7	$65.88	6.845%	$70.3895	$70.39	$70.40	$70.40
7 purchase totals =	$692.22		$729.2612	$729.26	$729.20	$729.40