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	$63.37	8.601%	$68.8205	$68.82	$68.80	$68.80
Purchase #2	$173.69	12.859%	$196.0248	$196.02	$196.00	$196.00
Purchase #3	$141.47	4.521%	$147.8659	$147.87	$147.85	$147.90
Purchase #4	$65.43	12.320%	$73.491	$73.49	$73.50	$73.50
Purchase #5	$129.99	11.829%	$145.3665	$145.37	$145.35	$145.40
Purchase #6	$142.44	8.502%	$154.5502	$154.55	$154.55	$154.60
Purchase #7	$236.72	11.646%	$264.2884	$264.29	$264.30	$264.30
7 purchase totals =	$953.11		$1,050.4073	$1,050.41	$1,050.35	$1,050.50