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	$185.75	5.136%	$195.2901	$195.29	$195.30	$195.30
Purchase #2	$53.53	11.780%	$59.8358	$59.84	$59.85	$59.80
Purchase #3	$139.35	12.634%	$156.9555	$156.96	$156.95	$157.00
Purchase #4	$97.28	3.163%	$100.357	$100.36	$100.35	$100.40
Purchase #5	$242.71	9.129%	$264.867	$264.87	$264.85	$264.90
Purchase #6	$227.77	6.632%	$242.8757	$242.88	$242.90	$242.90
Purchase #7	$180.49	4.196%	$188.0634	$188.06	$188.05	$188.10
7 purchase totals =	$1,126.88		$1,208.2445	$1,208.26	$1,208.25	$1,208.40