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	$46.60	4.175%	$48.5456	$48.55	$48.55	$48.50
Purchase #2	$105.73	12.190%	$118.6185	$118.62	$118.60	$118.60
Purchase #3	$201.26	5.502%	$212.3333	$212.33	$212.35	$212.30
Purchase #4	$49.69	12.596%	$55.949	$55.95	$55.95	$55.90
Purchase #5	$128.91	4.226%	$134.3577	$134.36	$134.35	$134.40
Purchase #6	$227.66	9.472%	$249.224	$249.22	$249.20	$249.20
Purchase #7	$189.88	3.470%	$196.4688	$196.47	$196.45	$196.50
7 purchase totals =	$949.73		$1,015.4969	$1,015.50	$1,015.45	$1,015.40