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	$80.28	11.190%	$89.2633	$89.26	$89.25	$89.30
Purchase #2	$144.83	11.343%	$161.2581	$161.26	$161.25	$161.30
Purchase #3	$169.60	9.746%	$186.1292	$186.13	$186.15	$186.10
Purchase #4	$90.86	4.188%	$94.6652	$94.67	$94.65	$94.70
Purchase #5	$184.61	11.647%	$206.1115	$206.11	$206.10	$206.10
Purchase #6	$150.73	4.669%	$157.7676	$157.77	$157.75	$157.80
Purchase #7	$184.81	6.303%	$196.4586	$196.46	$196.45	$196.50
7 purchase totals =	$1,005.72		$1,091.6535	$1,091.66	$1,091.60	$1,091.80