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	$250.38	5.674%	$264.5866	$264.59	$264.60	$264.60
Purchase #2	$150.98	6.579%	$160.913	$160.91	$160.90	$160.90
Purchase #3	$160.82	3.120%	$165.8376	$165.84	$165.85	$165.80
Purchase #4	$126.75	7.558%	$136.3298	$136.33	$136.35	$136.30
Purchase #5	$126.33	6.853%	$134.9874	$134.99	$135.00	$135.00
Purchase #6	$174.77	6.328%	$185.8294	$185.83	$185.85	$185.80
Purchase #7	$141.66	3.427%	$146.5147	$146.51	$146.50	$146.50
7 purchase totals =	$1,131.69		$1,194.9985	$1,195.00	$1,195.05	$1,194.90