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	$113.25	4.236%	$118.0473	$118.05	$118.05	$118.00
Purchase #2	$217.88	12.272%	$244.6182	$244.62	$244.60	$244.60
Purchase #3	$140.38	8.355%	$152.1087	$152.11	$152.10	$152.10
Purchase #4	$192.27	9.729%	$210.9759	$210.98	$211.00	$211.00
Purchase #5	$82.73	8.148%	$89.4708	$89.47	$89.45	$89.50
Purchase #6	$111.36	3.379%	$115.1229	$115.12	$115.10	$115.10
Purchase #7	$104.78	6.293%	$111.3738	$111.37	$111.35	$111.40
7 purchase totals =	$962.65		$1,041.7176	$1,041.72	$1,041.65	$1,041.70