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	$33.32	5.130%	$35.0293	$35.03	$35.05	$35.00
Purchase #2	$188.27	6.515%	$200.5358	$200.54	$200.55	$200.50
Purchase #3	$247.55	13.426%	$280.7861	$280.79	$280.80	$280.80
Purchase #4	$16.73	5.699%	$17.6834	$17.68	$17.70	$17.70
Purchase #5	$189.96	3.352%	$196.3275	$196.33	$196.35	$196.30
Purchase #6	$246.94	10.751%	$273.4885	$273.49	$273.50	$273.50
Purchase #7	$57.53	9.402%	$62.939	$62.94	$62.95	$62.90
7 purchase totals =	$980.30		$1,066.7896	$1,066.80	$1,066.90	$1,066.70