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	$236.68	5.654%	$250.0619	$250.06	$250.05	$250.10
Purchase #2	$58.41	5.586%	$61.6728	$61.67	$61.65	$61.70
Purchase #3	$196.26	7.740%	$211.4505	$211.45	$211.45	$211.50
Purchase #4	$139.27	12.360%	$156.4838	$156.48	$156.50	$156.50
Purchase #5	$210.29	6.312%	$223.5635	$223.56	$223.55	$223.60
Purchase #6	$244.77	7.322%	$262.6921	$262.69	$262.70	$262.70
Purchase #7	$174.82	6.278%	$185.7952	$185.80	$185.80	$185.80
7 purchase totals =	$1,260.50		$1,351.7198	$1,351.71	$1,351.70	$1,351.90