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	$154.56	10.564%	$170.8877	$170.89	$170.90	$170.90
Purchase #2	$145.38	11.528%	$162.1394	$162.14	$162.15	$162.10
Purchase #3	$159.31	13.715%	$181.1594	$181.16	$181.15	$181.20
Purchase #4	$28.39	13.696%	$32.2783	$32.28	$32.30	$32.30
Purchase #5	$244.86	13.549%	$278.0361	$278.04	$278.05	$278.00
Purchase #6	$194.37	7.543%	$209.0313	$209.03	$209.05	$209.00
Purchase #7	$97.53	11.704%	$108.9449	$108.94	$108.95	$108.90
7 purchase totals =	$1,024.40		$1,142.4771	$1,142.48	$1,142.55	$1,142.40