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	$154.50	6.737%	$164.9087	$164.91	$164.90	$164.90
Purchase #2	$157.29	3.497%	$162.7904	$162.79	$162.80	$162.80
Purchase #3	$67.31	4.464%	$70.3147	$70.31	$70.30	$70.30
Purchase #4	$235.64	6.472%	$250.8906	$250.89	$250.90	$250.90
Purchase #5	$129.85	7.280%	$139.3031	$139.30	$139.30	$139.30
Purchase #6	$31.77	6.222%	$33.7467	$33.75	$33.75	$33.70
Purchase #7	$62.58	3.179%	$64.5694	$64.57	$64.55	$64.60
7 purchase totals =	$838.94		$886.5236	$886.52	$886.50	$886.50