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	$190.52	11.535%	$212.4965	$212.50	$212.50	$212.50
Purchase #2	$78.69	9.476%	$86.1467	$86.15	$86.15	$86.10
Purchase #3	$19.39	5.814%	$20.5173	$20.52	$20.50	$20.50
Purchase #4	$9.48	5.846%	$10.0342	$10.03	$10.05	$10.00
Purchase #5	$160.36	3.436%	$165.87	$165.87	$165.85	$165.90
Purchase #6	$110.73	4.167%	$115.3441	$115.34	$115.35	$115.30
Purchase #7	$135.63	10.823%	$150.3092	$150.31	$150.30	$150.30
7 purchase totals =	$704.80		$760.7180	$760.72	$760.70	$760.60