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	$115.73	6.496%	$123.2478	$123.25	$123.25	$123.20
Purchase #2	$169.33	11.627%	$189.018	$189.02	$189.00	$189.00
Purchase #3	$208.33	4.303%	$217.2944	$217.29	$217.30	$217.30
Purchase #4	$232.63	3.187%	$240.0439	$240.04	$240.05	$240.00
Purchase #5	$23.59	3.830%	$24.4935	$24.49	$24.50	$24.50
Purchase #6	$40.39	13.380%	$45.7942	$45.79	$45.80	$45.80
Purchase #7	$99.91	4.498%	$104.404	$104.40	$104.40	$104.40
7 purchase totals =	$889.91		$944.2958	$944.28	$944.30	$944.20