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	$115.79	6.587%	$123.4171	$123.42	$123.40	$123.40
Purchase #2	$206.58	8.428%	$223.9906	$223.99	$224.00	$224.00
Purchase #3	$35.78	3.738%	$37.1175	$37.12	$37.10	$37.10
Purchase #4	$250.77	10.600%	$277.3516	$277.35	$277.35	$277.40
Purchase #5	$52.76	11.858%	$59.0163	$59.02	$59.00	$59.00
Purchase #6	$135.94	6.656%	$144.9882	$144.99	$145.00	$145.00
Purchase #7	$209.95	4.735%	$219.8911	$219.89	$219.90	$219.90
7 purchase totals =	$1,007.57		$1,085.7724	$1,085.78	$1,085.75	$1,085.80