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	$52.49	7.588%	$56.4729	$56.47	$56.45	$56.50
Purchase #2	$39.71	7.658%	$42.751	$42.75	$42.75	$42.80
Purchase #3	$12.70	10.571%	$14.0425	$14.04	$14.05	$14.00
Purchase #4	$118.46	4.139%	$123.3631	$123.36	$123.35	$123.40
Purchase #5	$74.28	12.803%	$83.7901	$83.79	$83.80	$83.80
Purchase #6	$202.27	4.868%	$212.1165	$212.12	$212.10	$212.10
Purchase #7	$56.26	11.742%	$62.866	$62.87	$62.85	$62.90
7 purchase totals =	$556.17		$595.4021	$595.40	$595.35	$595.50