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	$114.99	12.632%	$129.5155	$129.52	$129.50	$129.50
Purchase #2	$130.51	8.229%	$141.2497	$141.25	$141.25	$141.20
Purchase #3	$26.78	7.326%	$28.7419	$28.74	$28.75	$28.70
Purchase #4	$89.75	6.257%	$95.3657	$95.37	$95.35	$95.40
Purchase #5	$82.80	7.609%	$89.1003	$89.10	$89.10	$89.10
Purchase #6	$97.47	4.153%	$101.5179	$101.52	$101.50	$101.50
Purchase #7	$173.77	4.398%	$181.4124	$181.41	$181.40	$181.40
7 purchase totals =	$716.07		$766.9034	$766.91	$766.85	$766.80