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	$170.46	8.802%	$185.4639	$185.46	$185.45	$185.50
Purchase #2	$45.52	7.665%	$49.0091	$49.01	$49.00	$49.00
Purchase #3	$240.86	4.112%	$250.7642	$250.76	$250.75	$250.80
Purchase #4	$228.86	10.231%	$252.2747	$252.27	$252.25	$252.30
Purchase #5	$53.66	10.426%	$59.2546	$59.25	$59.25	$59.30
Purchase #6	$195.72	6.870%	$209.166	$209.17	$209.15	$209.20
Purchase #7	$8.90	4.471%	$9.2979	$9.30	$9.30	$9.30
7 purchase totals =	$943.98		$1,015.2304	$1,015.22	$1,015.15	$1,015.40