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	$50.80	6.362%	$54.0319	$54.03	$54.05	$54.00
Purchase #2	$201.77	6.184%	$214.2475	$214.25	$214.25	$214.20
Purchase #3	$80.29	7.583%	$86.3784	$86.38	$86.40	$86.40
Purchase #4	$91.46	8.782%	$99.492	$99.49	$99.50	$99.50
Purchase #5	$30.48	5.187%	$32.061	$32.06	$32.05	$32.10
Purchase #6	$156.43	3.842%	$162.44	$162.44	$162.45	$162.40
Purchase #7	$72.95	9.539%	$79.9087	$79.91	$79.90	$79.90
7 purchase totals =	$684.18		$728.5595	$728.56	$728.60	$728.50