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	$98.51	12.440%	$110.7646	$110.76	$110.75	$110.80
Purchase #2	$153.40	12.340%	$172.3296	$172.33	$172.35	$172.30
Purchase #3	$238.35	11.122%	$264.8593	$264.86	$264.85	$264.90
Purchase #4	$221.59	3.571%	$229.503	$229.50	$229.50	$229.50
Purchase #5	$190.88	10.814%	$211.5218	$211.52	$211.50	$211.50
Purchase #6	$60.90	10.589%	$67.3487	$67.35	$67.35	$67.30
Purchase #7	$183.47	10.379%	$202.5124	$202.51	$202.50	$202.50
7 purchase totals =	$1,147.10		$1,258.8394	$1,258.83	$1,258.80	$1,258.80