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	$182.65	3.443%	$188.9386	$188.94	$188.95	$188.90
Purchase #2	$94.49	11.248%	$105.1182	$105.12	$105.10	$105.10
Purchase #3	$49.34	8.655%	$53.6104	$53.61	$53.60	$53.60
Purchase #4	$32.65	13.507%	$37.06	$37.06	$37.05	$37.10
Purchase #5	$236.61	11.589%	$264.0307	$264.03	$264.05	$264.00
Purchase #6	$211.31	12.526%	$237.7787	$237.78	$237.80	$237.80
Purchase #7	$196.28	12.567%	$220.9465	$220.95	$220.95	$220.90
7 purchase totals =	$1,003.33		$1,107.4831	$1,107.49	$1,107.50	$1,107.40