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	$130.62	10.435%	$144.2502	$144.25	$144.25	$144.30
Purchase #2	$158.42	3.870%	$164.5509	$164.55	$164.55	$164.60
Purchase #3	$68.52	12.775%	$77.2734	$77.27	$77.25	$77.30
Purchase #4	$130.73	11.623%	$145.9247	$145.92	$145.90	$145.90
Purchase #5	$85.46	7.776%	$92.1054	$92.11	$92.10	$92.10
Purchase #6	$80.74	10.241%	$89.0086	$89.01	$89.00	$89.00
Purchase #7	$199.89	9.677%	$219.2334	$219.23	$219.25	$219.20
7 purchase totals =	$854.38		$932.3466	$932.34	$932.30	$932.40