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	$86.38	7.489%	$92.849	$92.85	$92.85	$92.80
Purchase #2	$209.35	3.614%	$216.9159	$216.92	$216.90	$216.90
Purchase #3	$219.85	13.287%	$249.0615	$249.06	$249.05	$249.10
Purchase #4	$148.95	5.297%	$156.8399	$156.84	$156.85	$156.80
Purchase #5	$110.48	8.196%	$119.5349	$119.53	$119.55	$119.50
Purchase #6	$33.33	6.693%	$35.5608	$35.56	$35.55	$35.60
Purchase #7	$62.54	7.851%	$67.45	$67.45	$67.45	$67.50
7 purchase totals =	$870.88		$938.2120	$938.21	$938.20	$938.20