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	$55.68	4.815%	$58.361	$58.36	$58.35	$58.40
Purchase #2	$90.53	8.872%	$98.5618	$98.56	$98.55	$98.60
Purchase #3	$49.36	9.597%	$54.0971	$54.10	$54.10	$54.10
Purchase #4	$130.46	5.331%	$137.4148	$137.41	$137.40	$137.40
Purchase #5	$162.97	13.768%	$185.4077	$185.41	$185.40	$185.40
Purchase #6	$115.64	6.778%	$123.4781	$123.48	$123.50	$123.50
Purchase #7	$137.31	9.681%	$150.603	$150.60	$150.60	$150.60
7 purchase totals =	$741.95		$807.9235	$807.92	$807.90	$808.00