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	$54.59	3.199%	$56.3363	$56.34	$56.35	$56.30
Purchase #2	$104.62	4.534%	$109.3635	$109.36	$109.35	$109.40
Purchase #3	$93.43	3.575%	$96.7701	$96.77	$96.75	$96.80
Purchase #4	$125.25	12.329%	$140.6921	$140.69	$140.70	$140.70
Purchase #5	$137.76	12.591%	$155.1054	$155.11	$155.10	$155.10
Purchase #6	$72.50	10.569%	$80.1625	$80.16	$80.15	$80.20
Purchase #7	$196.32	10.628%	$217.1849	$217.18	$217.20	$217.20
7 purchase totals =	$784.47		$855.6148	$855.61	$855.60	$855.70