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	$156.67	10.649%	$173.3538	$173.35	$173.35	$173.40
Purchase #2	$218.69	12.746%	$246.5642	$246.56	$246.55	$246.60
Purchase #3	$93.57	10.435%	$103.334	$103.33	$103.35	$103.30
Purchase #4	$65.72	4.301%	$68.5466	$68.55	$68.55	$68.50
Purchase #5	$187.27	7.282%	$200.907	$200.91	$200.90	$200.90
Purchase #6	$30.54	10.450%	$33.7314	$33.73	$33.75	$33.70
Purchase #7	$182.44	5.206%	$191.9378	$191.94	$191.95	$191.90
7 purchase totals =	$934.90		$1,018.3748	$1,018.37	$1,018.40	$1,018.30