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	$94.93	7.686%	$102.2263	$102.23	$102.25	$102.20
Purchase #2	$164.67	11.561%	$183.7075	$183.71	$183.70	$183.70
Purchase #3	$162.50	5.396%	$171.2685	$171.27	$171.25	$171.30
Purchase #4	$157.73	9.542%	$172.7806	$172.78	$172.80	$172.80
Purchase #5	$243.50	8.599%	$264.4386	$264.44	$264.45	$264.40
Purchase #6	$94.75	9.570%	$103.8176	$103.82	$103.80	$103.80
Purchase #7	$94.43	7.421%	$101.4377	$101.44	$101.45	$101.40
7 purchase totals =	$1,012.51		$1,099.6768	$1,099.69	$1,099.70	$1,099.60