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	$134.98	5.555%	$142.4781	$142.48	$142.50	$142.50
Purchase #2	$40.69	3.456%	$42.0962	$42.10	$42.10	$42.10
Purchase #3	$92.66	3.321%	$95.7372	$95.74	$95.75	$95.70
Purchase #4	$78.28	9.709%	$85.8802	$85.88	$85.90	$85.90
Purchase #5	$154.61	11.410%	$172.251	$172.25	$172.25	$172.30
Purchase #6	$209.39	3.198%	$216.0863	$216.09	$216.10	$216.10
Purchase #7	$95.46	4.205%	$99.4741	$99.47	$99.45	$99.50
7 purchase totals =	$806.07		$854.0031	$854.01	$854.05	$854.10