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	$55.29	12.744%	$62.3362	$62.34	$62.35	$62.30
Purchase #2	$178.41	12.441%	$200.606	$200.61	$200.60	$200.60
Purchase #3	$146.30	3.816%	$151.8828	$151.88	$151.90	$151.90
Purchase #4	$218.91	5.251%	$230.405	$230.41	$230.40	$230.40
Purchase #5	$21.76	12.198%	$24.4143	$24.41	$24.40	$24.40
Purchase #6	$82.28	4.486%	$85.9711	$85.97	$85.95	$86.00
Purchase #7	$49.48	11.151%	$54.9975	$55.00	$55.00	$55.00
7 purchase totals =	$752.43		$810.6129	$810.62	$810.60	$810.60