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	$130.60	11.265%	$145.3121	$145.31	$145.30	$145.30
Purchase #2	$99.57	13.414%	$112.9263	$112.93	$112.95	$112.90
Purchase #3	$42.32	7.270%	$45.3967	$45.40	$45.40	$45.40
Purchase #4	$196.49	7.227%	$210.6903	$210.69	$210.70	$210.70
Purchase #5	$59.67	7.695%	$64.2616	$64.26	$64.25	$64.30
Purchase #6	$31.56	6.327%	$33.5568	$33.56	$33.55	$33.60
Purchase #7	$229.49	9.691%	$251.7299	$251.73	$251.75	$251.70
7 purchase totals =	$789.70		$863.8737	$863.88	$863.90	$863.90