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	$182.44	11.304%	$203.063	$203.06	$203.05	$203.10
Purchase #2	$85.31	13.373%	$96.7185	$96.72	$96.70	$96.70
Purchase #3	$53.60	11.503%	$59.7656	$59.77	$59.75	$59.80
Purchase #4	$182.70	7.399%	$196.218	$196.22	$196.20	$196.20
Purchase #5	$60.69	5.180%	$63.8337	$63.83	$63.85	$63.80
Purchase #6	$146.81	9.374%	$160.572	$160.57	$160.55	$160.60
Purchase #7	$40.30	13.735%	$45.8352	$45.84	$45.85	$45.80
7 purchase totals =	$751.85		$826.0060	$826.01	$825.95	$826.00