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	$98.27	5.333%	$103.5107	$103.51	$103.50	$103.50
Purchase #2	$166.42	11.507%	$185.5699	$185.57	$185.55	$185.60
Purchase #3	$78.28	3.409%	$80.9486	$80.95	$80.95	$80.90
Purchase #4	$85.73	3.175%	$88.4519	$88.45	$88.45	$88.50
Purchase #5	$100.49	8.578%	$109.11	$109.11	$109.10	$109.10
Purchase #6	$190.50	8.401%	$206.5039	$206.50	$206.50	$206.50
Purchase #7	$24.79	5.127%	$26.061	$26.06	$26.05	$26.10
7 purchase totals =	$744.48		$800.1560	$800.15	$800.10	$800.20