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	$77.66	7.398%	$83.4053	$83.41	$83.40	$83.40
Purchase #2	$112.37	11.711%	$125.5297	$125.53	$125.55	$125.50
Purchase #3	$226.52	9.475%	$247.9828	$247.98	$248.00	$248.00
Purchase #4	$154.76	13.669%	$175.9141	$175.91	$175.90	$175.90
Purchase #5	$191.35	6.322%	$203.4471	$203.45	$203.45	$203.40
Purchase #6	$40.25	13.327%	$45.6141	$45.61	$45.60	$45.60
Purchase #7	$228.69	7.521%	$245.8898	$245.89	$245.90	$245.90
7 purchase totals =	$1,031.60		$1,127.7829	$1,127.78	$1,127.80	$1,127.70