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	$130.74	8.177%	$141.4306	$141.43	$141.45	$141.40
Purchase #2	$111.48	3.272%	$115.1276	$115.13	$115.15	$115.10
Purchase #3	$91.36	9.481%	$100.0218	$100.02	$100.00	$100.00
Purchase #4	$34.75	4.813%	$36.4225	$36.42	$36.40	$36.40
Purchase #5	$67.83	7.593%	$72.9803	$72.98	$73.00	$73.00
Purchase #6	$131.42	9.589%	$144.0219	$144.02	$144.00	$144.00
Purchase #7	$113.33	9.809%	$124.4465	$124.45	$124.45	$124.40
7 purchase totals =	$680.91		$734.4512	$734.45	$734.45	$734.30