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	$199.71	11.367%	$222.411	$222.41	$222.40	$222.40
Purchase #2	$181.98	13.217%	$206.0323	$206.03	$206.05	$206.00
Purchase #3	$30.77	13.793%	$35.0141	$35.01	$35.00	$35.00
Purchase #4	$211.66	5.475%	$223.2484	$223.25	$223.25	$223.20
Purchase #5	$157.46	11.108%	$174.9507	$174.95	$174.95	$175.00
Purchase #6	$94.70	4.423%	$98.8886	$98.89	$98.90	$98.90
Purchase #7	$38.56	5.214%	$40.5705	$40.57	$40.55	$40.60
7 purchase totals =	$914.84		$1,001.1156	$1,001.11	$1,001.10	$1,001.10