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	$193.62	11.860%	$216.5833	$216.58	$216.60	$216.60
Purchase #2	$6.92	3.520%	$7.1636	$7.16	$7.15	$7.20
Purchase #3	$104.32	5.286%	$109.8344	$109.83	$109.85	$109.80
Purchase #4	$77.65	6.725%	$82.872	$82.87	$82.85	$82.90
Purchase #5	$210.33	5.293%	$221.4628	$221.46	$221.45	$221.50
Purchase #6	$85.46	3.441%	$88.4007	$88.40	$88.40	$88.40
Purchase #7	$137.26	9.872%	$150.8103	$150.81	$150.80	$150.80
7 purchase totals =	$815.56		$877.1271	$877.11	$877.10	$877.20