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	$240.86	4.158%	$250.875	$250.88	$250.90	$250.90
Purchase #2	$6.86	3.837%	$7.1232	$7.12	$7.10	$7.10
Purchase #3	$98.54	6.212%	$104.6613	$104.66	$104.65	$104.70
Purchase #4	$187.82	10.168%	$206.9175	$206.92	$206.90	$206.90
Purchase #5	$211.55	5.754%	$223.7226	$223.72	$223.70	$223.70
Purchase #6	$37.92	9.443%	$41.5008	$41.50	$41.50	$41.50
Purchase #7	$86.91	11.480%	$96.8873	$96.89	$96.90	$96.90
7 purchase totals =	$870.46		$931.6877	$931.69	$931.65	$931.70