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	$93.32	12.791%	$105.2566	$105.26	$105.25	$105.30
Purchase #2	$129.36	11.420%	$144.1329	$144.13	$144.15	$144.10
Purchase #3	$191.54	9.199%	$209.1598	$209.16	$209.15	$209.20
Purchase #4	$245.68	9.233%	$268.3636	$268.36	$268.35	$268.40
Purchase #5	$231.60	9.501%	$253.6043	$253.60	$253.60	$253.60
Purchase #6	$82.72	10.460%	$91.3725	$91.37	$91.35	$91.40
Purchase #7	$30.46	4.759%	$31.9096	$31.91	$31.90	$31.90
7 purchase totals =	$1,004.68		$1,103.7993	$1,103.79	$1,103.75	$1,103.90