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	$122.77	6.399%	$130.6261	$130.63	$130.65	$130.60
Purchase #2	$208.65	3.644%	$216.2532	$216.25	$216.25	$216.30
Purchase #3	$133.74	6.184%	$142.0105	$142.01	$142.00	$142.00
Purchase #4	$136.69	4.238%	$142.4829	$142.48	$142.50	$142.50
Purchase #5	$85.71	12.386%	$96.326	$96.33	$96.35	$96.30
Purchase #6	$142.73	5.229%	$150.1934	$150.19	$150.20	$150.20
Purchase #7	$244.49	8.460%	$265.1739	$265.17	$265.15	$265.20
7 purchase totals =	$1,074.78		$1,143.0660	$1,143.06	$1,143.10	$1,143.10