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	$158.94	9.741%	$174.4223	$174.42	$174.40	$174.40
Purchase #2	$92.28	13.761%	$104.9787	$104.98	$105.00	$105.00
Purchase #3	$26.58	9.509%	$29.1075	$29.11	$29.10	$29.10
Purchase #4	$88.93	11.398%	$99.0662	$99.07	$99.05	$99.10
Purchase #5	$115.80	10.581%	$128.0528	$128.05	$128.05	$128.10
Purchase #6	$81.51	6.603%	$86.8921	$86.89	$86.90	$86.90
Purchase #7	$27.65	3.600%	$28.6454	$28.65	$28.65	$28.60
7 purchase totals =	$591.69		$651.1650	$651.17	$651.15	$651.20