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	$147.94	13.834%	$168.406	$168.41	$168.40	$168.40
Purchase #2	$136.79	7.154%	$146.576	$146.58	$146.60	$146.60
Purchase #3	$43.30	4.581%	$45.2836	$45.28	$45.30	$45.30
Purchase #4	$154.69	7.751%	$166.68	$166.68	$166.70	$166.70
Purchase #5	$25.46	11.482%	$28.3833	$28.38	$28.40	$28.40
Purchase #6	$198.92	9.741%	$218.2968	$218.30	$218.30	$218.30
Purchase #7	$80.27	6.849%	$85.7677	$85.77	$85.75	$85.80
7 purchase totals =	$787.37		$859.3934	$859.40	$859.45	$859.50