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	$242.53	6.736%	$258.8668	$258.87	$258.85	$258.90
Purchase #2	$166.54	11.581%	$185.827	$185.83	$185.85	$185.80
Purchase #3	$185.28	4.700%	$193.9882	$193.99	$194.00	$194.00
Purchase #4	$80.81	3.816%	$83.8937	$83.89	$83.90	$83.90
Purchase #5	$170.41	6.789%	$181.9791	$181.98	$182.00	$182.00
Purchase #6	$147.31	6.668%	$157.1326	$157.13	$157.15	$157.10
Purchase #7	$154.80	7.410%	$166.2707	$166.27	$166.25	$166.30
7 purchase totals =	$1,147.68		$1,227.9581	$1,227.96	$1,228.00	$1,228.00