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	$246.51	9.346%	$269.5488	$269.55	$269.55	$269.50
Purchase #2	$61.38	11.501%	$68.4393	$68.44	$68.45	$68.40
Purchase #3	$104.64	6.816%	$111.7723	$111.77	$111.75	$111.80
Purchase #4	$245.37	13.565%	$278.6544	$278.65	$278.65	$278.70
Purchase #5	$144.27	6.356%	$153.4398	$153.44	$153.45	$153.40
Purchase #6	$30.40	3.568%	$31.4847	$31.48	$31.50	$31.50
Purchase #7	$142.68	7.246%	$153.0186	$153.02	$153.00	$153.00
7 purchase totals =	$975.25		$1,066.3579	$1,066.35	$1,066.35	$1,066.30