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	$31.77	10.348%	$35.0576	$35.06	$35.05	$35.10
Purchase #2	$24.36	11.309%	$27.1149	$27.11	$27.10	$27.10
Purchase #3	$215.75	10.466%	$238.3304	$238.33	$238.35	$238.30
Purchase #4	$136.84	8.435%	$148.3825	$148.38	$148.40	$148.40
Purchase #5	$146.76	5.619%	$155.0064	$155.01	$155.00	$155.00
Purchase #6	$170.34	8.859%	$185.4304	$185.43	$185.45	$185.40
Purchase #7	$170.69	5.308%	$179.7502	$179.75	$179.75	$179.80
7 purchase totals =	$896.51		$969.0724	$969.07	$969.10	$969.10