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	$243.41	10.779%	$269.6472	$269.65	$269.65	$269.60
Purchase #2	$220.42	8.872%	$239.9757	$239.98	$240.00	$240.00
Purchase #3	$35.62	4.735%	$37.3066	$37.31	$37.30	$37.30
Purchase #4	$9.93	6.834%	$10.6086	$10.61	$10.60	$10.60
Purchase #5	$84.49	12.198%	$94.7961	$94.80	$94.80	$94.80
Purchase #6	$245.72	7.570%	$264.321	$264.32	$264.30	$264.30
Purchase #7	$128.89	12.210%	$144.6275	$144.63	$144.65	$144.60
7 purchase totals =	$968.48		$1,061.2827	$1,061.30	$1,061.30	$1,061.20