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	$134.61	13.558%	$152.8604	$152.86	$152.85	$152.90
Purchase #2	$170.75	4.680%	$178.7411	$178.74	$178.75	$178.70
Purchase #3	$180.43	8.668%	$196.0697	$196.07	$196.05	$196.10
Purchase #4	$238.51	4.127%	$248.3533	$248.35	$248.35	$248.40
Purchase #5	$167.65	12.512%	$188.6264	$188.63	$188.65	$188.60
Purchase #6	$69.43	4.860%	$72.8043	$72.80	$72.80	$72.80
Purchase #7	$244.92	6.512%	$260.8692	$260.87	$260.85	$260.90
7 purchase totals =	$1,206.30		$1,298.3244	$1,298.32	$1,298.30	$1,298.40