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	$157.35	11.245%	$175.044	$175.04	$175.05	$175.00
Purchase #2	$168.84	9.667%	$185.1618	$185.16	$185.15	$185.20
Purchase #3	$58.27	12.467%	$65.5345	$65.53	$65.55	$65.50
Purchase #4	$66.46	10.185%	$73.229	$73.23	$73.25	$73.20
Purchase #5	$82.49	8.330%	$89.3614	$89.36	$89.35	$89.40
Purchase #6	$194.29	7.143%	$208.1681	$208.17	$208.15	$208.20
Purchase #7	$23.98	13.801%	$27.2895	$27.29	$27.30	$27.30
7 purchase totals =	$751.68		$823.7883	$823.78	$823.80	$823.80