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	$71.48	3.492%	$73.9761	$73.98	$74.00	$74.00
Purchase #2	$41.52	9.194%	$45.3373	$45.34	$45.35	$45.30
Purchase #3	$248.60	5.208%	$261.5471	$261.55	$261.55	$261.50
Purchase #4	$107.88	13.730%	$122.6919	$122.69	$122.70	$122.70
Purchase #5	$54.56	3.449%	$56.4418	$56.44	$56.45	$56.40
Purchase #6	$229.93	13.400%	$260.7406	$260.74	$260.75	$260.70
Purchase #7	$182.31	7.853%	$196.6268	$196.63	$196.65	$196.60
7 purchase totals =	$936.28		$1,017.3616	$1,017.37	$1,017.45	$1,017.20