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	$105.57	6.747%	$112.6928	$112.69	$112.70	$112.70
Purchase #2	$19.75	3.862%	$20.5127	$20.51	$20.50	$20.50
Purchase #3	$47.27	8.148%	$51.1216	$51.12	$51.10	$51.10
Purchase #4	$74.35	8.768%	$80.869	$80.87	$80.85	$80.90
Purchase #5	$37.30	9.551%	$40.8625	$40.86	$40.85	$40.90
Purchase #6	$52.60	5.517%	$55.5019	$55.50	$55.50	$55.50
Purchase #7	$150.36	6.748%	$160.5063	$160.51	$160.50	$160.50
7 purchase totals =	$487.20		$522.0668	$522.06	$522.00	$522.10