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	$39.90	13.434%	$45.2602	$45.26	$45.25	$45.30
Purchase #2	$69.86	6.112%	$74.1298	$74.13	$74.15	$74.10
Purchase #3	$224.94	11.415%	$250.6169	$250.62	$250.60	$250.60
Purchase #4	$175.55	5.844%	$185.8091	$185.81	$185.80	$185.80
Purchase #5	$127.56	13.559%	$144.8559	$144.86	$144.85	$144.90
Purchase #6	$239.46	4.589%	$250.4488	$250.45	$250.45	$250.40
Purchase #7	$56.42	6.173%	$59.9028	$59.90	$59.90	$59.90
7 purchase totals =	$933.69		$1,011.0235	$1,011.03	$1,011.00	$1,011.00