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	$176.28	10.219%	$194.2941	$194.29	$194.30	$194.30
Purchase #2	$96.77	8.666%	$105.1561	$105.16	$105.15	$105.20
Purchase #3	$81.61	10.806%	$90.4288	$90.43	$90.45	$90.40
Purchase #4	$225.33	6.112%	$239.1022	$239.10	$239.10	$239.10
Purchase #5	$137.80	13.857%	$156.8949	$156.89	$156.90	$156.90
Purchase #6	$181.68	4.601%	$190.0391	$190.04	$190.05	$190.00
Purchase #7	$23.76	11.672%	$26.5333	$26.53	$26.55	$26.50
7 purchase totals =	$923.23		$1,002.4485	$1,002.44	$1,002.50	$1,002.40