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	$164.26	6.729%	$175.3131	$175.31	$175.30	$175.30
Purchase #2	$70.92	9.492%	$77.6517	$77.65	$77.65	$77.70
Purchase #3	$92.66	12.166%	$103.933	$103.93	$103.95	$103.90
Purchase #4	$110.82	11.492%	$123.5554	$123.56	$123.55	$123.60
Purchase #5	$39.92	4.710%	$41.8002	$41.80	$41.80	$41.80
Purchase #6	$237.53	5.598%	$250.8269	$250.83	$250.85	$250.80
Purchase #7	$48.75	12.289%	$54.7409	$54.74	$54.75	$54.70
7 purchase totals =	$764.86		$827.8212	$827.82	$827.85	$827.80