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	$152.76	13.184%	$172.8999	$172.90	$172.90	$172.90
Purchase #2	$183.31	6.590%	$195.3901	$195.39	$195.40	$195.40
Purchase #3	$184.69	12.220%	$207.2591	$207.26	$207.25	$207.30
Purchase #4	$215.72	3.134%	$222.4807	$222.48	$222.50	$222.50
Purchase #5	$165.60	11.318%	$184.3426	$184.34	$184.35	$184.30
Purchase #6	$179.92	6.220%	$191.111	$191.11	$191.10	$191.10
Purchase #7	$92.82	12.730%	$104.636	$104.64	$104.65	$104.60
7 purchase totals =	$1,174.82		$1,278.1194	$1,278.12	$1,278.15	$1,278.10