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	$178.45	7.688%	$192.1692	$192.17	$192.15	$192.20
Purchase #2	$50.94	5.817%	$53.9032	$53.90	$53.90	$53.90
Purchase #3	$48.74	10.334%	$53.7768	$53.78	$53.80	$53.80
Purchase #4	$83.87	3.138%	$86.5018	$86.50	$86.50	$86.50
Purchase #5	$220.43	4.150%	$229.5778	$229.58	$229.60	$229.60
Purchase #6	$191.75	11.515%	$213.83	$213.83	$213.85	$213.80
Purchase #7	$199.42	10.476%	$220.3112	$220.31	$220.30	$220.30
7 purchase totals =	$973.60		$1,050.0700	$1,050.07	$1,050.10	$1,050.10