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	$21.57	11.507%	$24.0521	$24.05	$24.05	$24.10
Purchase #2	$173.26	10.433%	$191.3362	$191.34	$191.35	$191.30
Purchase #3	$130.26	3.356%	$134.6315	$134.63	$134.65	$134.60
Purchase #4	$85.73	5.424%	$90.38	$90.38	$90.40	$90.40
Purchase #5	$155.28	9.806%	$170.5068	$170.51	$170.50	$170.50
Purchase #6	$218.32	3.823%	$226.6664	$226.67	$226.65	$226.70
Purchase #7	$182.91	7.405%	$196.4545	$196.45	$196.45	$196.50
7 purchase totals =	$967.33		$1,034.0275	$1,034.03	$1,034.05	$1,034.10