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	$103.58	11.782%	$115.7838	$115.78	$115.80	$115.80
Purchase #2	$36.52	3.295%	$37.7233	$37.72	$37.70	$37.70
Purchase #3	$192.87	6.576%	$205.5531	$205.55	$205.55	$205.60
Purchase #4	$26.88	5.332%	$28.3132	$28.31	$28.30	$28.30
Purchase #5	$142.26	4.585%	$148.7826	$148.78	$148.80	$148.80
Purchase #6	$34.83	6.874%	$37.2242	$37.22	$37.20	$37.20
Purchase #7	$144.98	12.119%	$162.5501	$162.55	$162.55	$162.60
7 purchase totals =	$681.92		$735.9303	$735.91	$735.90	$736.00