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	$156.60	9.871%	$172.058	$172.06	$172.05	$172.10
Purchase #2	$196.73	9.677%	$215.7676	$215.77	$215.75	$215.80
Purchase #3	$155.37	6.508%	$165.4815	$165.48	$165.50	$165.50
Purchase #4	$6.89	3.541%	$7.134	$7.13	$7.15	$7.10
Purchase #5	$89.32	6.830%	$95.4206	$95.42	$95.40	$95.40
Purchase #6	$182.89	11.285%	$203.5291	$203.53	$203.55	$203.50
Purchase #7	$30.62	10.339%	$33.7858	$33.79	$33.80	$33.80
7 purchase totals =	$818.42		$893.1766	$893.18	$893.20	$893.20