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	$219.30	8.802%	$238.6028	$238.60	$238.60	$238.60
Purchase #2	$242.51	6.450%	$258.1519	$258.15	$258.15	$258.20
Purchase #3	$82.95	4.295%	$86.5127	$86.51	$86.50	$86.50
Purchase #4	$113.28	7.840%	$122.1612	$122.16	$122.15	$122.20
Purchase #5	$85.94	4.328%	$89.6595	$89.66	$89.65	$89.70
Purchase #6	$106.91	8.316%	$115.8006	$115.80	$115.80	$115.80
Purchase #7	$126.35	10.250%	$139.3009	$139.30	$139.30	$139.30
7 purchase totals =	$977.24		$1,050.1896	$1,050.18	$1,050.15	$1,050.30