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	$68.44	7.768%	$73.7564	$73.76	$73.75	$73.80
Purchase #2	$191.53	10.593%	$211.8188	$211.82	$211.80	$211.80
Purchase #3	$179.40	13.766%	$204.0962	$204.10	$204.10	$204.10
Purchase #4	$57.84	11.150%	$64.2892	$64.29	$64.30	$64.30
Purchase #5	$176.51	6.777%	$188.4721	$188.47	$188.45	$188.50
Purchase #6	$83.68	6.773%	$89.3476	$89.35	$89.35	$89.30
Purchase #7	$227.42	10.180%	$250.5714	$250.57	$250.55	$250.60
7 purchase totals =	$984.82		$1,082.3517	$1,082.36	$1,082.30	$1,082.40