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	$106.54	8.417%	$115.5075	$115.51	$115.50	$115.50
Purchase #2	$86.28	7.152%	$92.4507	$92.45	$92.45	$92.50
Purchase #3	$40.82	3.274%	$42.1564	$42.16	$42.15	$42.20
Purchase #4	$51.56	9.488%	$56.452	$56.45	$56.45	$56.50
Purchase #5	$82.44	8.375%	$89.3444	$89.34	$89.35	$89.30
Purchase #6	$208.62	13.737%	$237.2781	$237.28	$237.30	$237.30
Purchase #7	$162.40	11.622%	$181.2741	$181.27	$181.25	$181.30
7 purchase totals =	$738.66		$814.4632	$814.46	$814.45	$814.60