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	$243.81	8.333%	$264.1267	$264.13	$264.15	$264.10
Purchase #2	$98.69	7.253%	$105.848	$105.85	$105.85	$105.80
Purchase #3	$53.85	11.872%	$60.2431	$60.24	$60.25	$60.20
Purchase #4	$223.46	13.564%	$253.7701	$253.77	$253.75	$253.80
Purchase #5	$20.88	3.501%	$21.611	$21.61	$21.60	$21.60
Purchase #6	$80.28	12.561%	$90.364	$90.36	$90.35	$90.40
Purchase #7	$189.53	8.705%	$206.0286	$206.03	$206.05	$206.00
7 purchase totals =	$910.50		$1,001.9915	$1,001.99	$1,002.00	$1,001.90