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	$193.99	5.608%	$204.869	$204.87	$204.85	$204.90
Purchase #2	$160.27	5.150%	$168.5239	$168.52	$168.50	$168.50
Purchase #3	$71.53	9.810%	$78.5471	$78.55	$78.55	$78.50
Purchase #4	$117.84	12.603%	$132.6914	$132.69	$132.70	$132.70
Purchase #5	$181.35	9.664%	$198.8757	$198.88	$198.90	$198.90
Purchase #6	$232.74	3.302%	$240.4251	$240.43	$240.45	$240.40
Purchase #7	$77.51	8.225%	$83.8852	$83.89	$83.90	$83.90
7 purchase totals =	$1,035.23		$1,107.8174	$1,107.83	$1,107.85	$1,107.80