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	$144.81	10.565%	$160.1092	$160.11	$160.10	$160.10
Purchase #2	$147.45	6.238%	$156.6479	$156.65	$156.65	$156.60
Purchase #3	$174.40	6.260%	$185.3174	$185.32	$185.30	$185.30
Purchase #4	$54.59	8.275%	$59.1073	$59.11	$59.10	$59.10
Purchase #5	$249.72	11.252%	$277.8185	$277.82	$277.80	$277.80
Purchase #6	$16.58	12.646%	$18.6767	$18.68	$18.70	$18.70
Purchase #7	$112.83	11.107%	$125.362	$125.36	$125.35	$125.40
7 purchase totals =	$900.38		$983.0390	$983.05	$983.00	$983.00