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	$147.43	11.827%	$164.8665	$164.87	$164.85	$164.90
Purchase #2	$104.88	13.142%	$118.6633	$118.66	$118.65	$118.70
Purchase #3	$196.36	4.171%	$204.5502	$204.55	$204.55	$204.60
Purchase #4	$92.29	7.425%	$99.1425	$99.14	$99.15	$99.10
Purchase #5	$181.61	4.774%	$190.2801	$190.28	$190.30	$190.30
Purchase #6	$213.54	11.300%	$237.67	$237.67	$237.65	$237.70
Purchase #7	$104.92	3.729%	$108.8325	$108.83	$108.85	$108.80
7 purchase totals =	$1,041.03		$1,124.0051	$1,124.00	$1,124.00	$1,124.10