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	$245.52	11.551%	$273.88	$273.88	$273.90	$273.90
Purchase #2	$53.48	12.453%	$60.1399	$60.14	$60.15	$60.10
Purchase #3	$81.71	10.478%	$90.2716	$90.27	$90.25	$90.30
Purchase #4	$46.76	9.252%	$51.0862	$51.09	$51.10	$51.10
Purchase #5	$172.81	4.120%	$179.9298	$179.93	$179.95	$179.90
Purchase #6	$104.44	5.580%	$110.2678	$110.27	$110.25	$110.30
Purchase #7	$219.74	5.246%	$231.2676	$231.27	$231.25	$231.30
7 purchase totals =	$924.46		$996.8429	$996.85	$996.85	$996.90