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	$194.69	4.447%	$203.3479	$203.35	$203.35	$203.30
Purchase #2	$145.35	4.598%	$152.0332	$152.03	$152.05	$152.00
Purchase #3	$30.31	8.690%	$32.9439	$32.94	$32.95	$32.90
Purchase #4	$69.33	4.336%	$72.3361	$72.34	$72.35	$72.30
Purchase #5	$202.66	9.482%	$221.8762	$221.88	$221.90	$221.90
Purchase #6	$233.88	12.166%	$262.3338	$262.33	$262.35	$262.30
Purchase #7	$48.54	12.218%	$54.4706	$54.47	$54.45	$54.50
7 purchase totals =	$924.76		$999.3417	$999.34	$999.40	$999.20