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	$162.71	5.108%	$171.0212	$171.02	$171.00	$171.00
Purchase #2	$92.77	4.348%	$96.8036	$96.80	$96.80	$96.80
Purchase #3	$109.56	5.406%	$115.4828	$115.48	$115.50	$115.50
Purchase #4	$78.83	6.492%	$83.9476	$83.95	$83.95	$83.90
Purchase #5	$24.33	10.546%	$26.8958	$26.90	$26.90	$26.90
Purchase #6	$56.41	4.699%	$59.0607	$59.06	$59.05	$59.10
Purchase #7	$27.65	4.705%	$28.9509	$28.95	$28.95	$29.00
7 purchase totals =	$552.26		$582.1626	$582.16	$582.15	$582.20