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	$156.76	6.483%	$166.9228	$166.92	$166.90	$166.90
Purchase #2	$245.76	13.230%	$278.274	$278.27	$278.25	$278.30
Purchase #3	$188.55	7.785%	$203.2286	$203.23	$203.25	$203.20
Purchase #4	$33.48	4.176%	$34.8781	$34.88	$34.90	$34.90
Purchase #5	$82.70	3.823%	$85.8616	$85.86	$85.85	$85.90
Purchase #6	$181.92	13.705%	$206.8521	$206.85	$206.85	$206.90
Purchase #7	$45.89	4.168%	$47.8027	$47.80	$47.80	$47.80
7 purchase totals =	$935.06		$1,023.8199	$1,023.81	$1,023.80	$1,023.90