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	$83.85	11.577%	$93.5573	$93.56	$93.55	$93.60
Purchase #2	$58.42	4.543%	$61.074	$61.07	$61.05	$61.10
Purchase #3	$98.65	3.871%	$102.4687	$102.47	$102.45	$102.50
Purchase #4	$165.98	5.114%	$174.4682	$174.47	$174.45	$174.50
Purchase #5	$76.37	11.634%	$85.2549	$85.25	$85.25	$85.30
Purchase #6	$31.31	7.772%	$33.7434	$33.74	$33.75	$33.70
Purchase #7	$152.35	6.534%	$162.3045	$162.30	$162.30	$162.30
7 purchase totals =	$666.93		$712.8710	$712.86	$712.80	$713.00