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	$40.86	12.273%	$45.8747	$45.87	$45.85	$45.90
Purchase #2	$237.32	11.113%	$263.6934	$263.69	$263.70	$263.70
Purchase #3	$170.73	8.367%	$185.015	$185.02	$185.00	$185.00
Purchase #4	$191.98	11.732%	$214.5031	$214.50	$214.50	$214.50
Purchase #5	$82.70	4.617%	$86.5183	$86.52	$86.50	$86.50
Purchase #6	$179.59	9.363%	$196.405	$196.41	$196.40	$196.40
Purchase #7	$168.98	3.160%	$174.3198	$174.32	$174.30	$174.30
7 purchase totals =	$1,072.16		$1,166.3293	$1,166.33	$1,166.25	$1,166.30