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	$248.73	3.858%	$258.326	$258.33	$258.35	$258.30
Purchase #2	$149.64	7.367%	$160.664	$160.66	$160.65	$160.70
Purchase #3	$160.42	6.699%	$171.1665	$171.17	$171.15	$171.20
Purchase #4	$221.28	11.199%	$246.0611	$246.06	$246.05	$246.10
Purchase #5	$149.33	11.834%	$167.0017	$167.00	$167.00	$167.00
Purchase #6	$95.50	5.121%	$100.3906	$100.39	$100.40	$100.40
Purchase #7	$176.45	11.405%	$196.5741	$196.57	$196.55	$196.60
7 purchase totals =	$1,201.35		$1,300.1840	$1,300.18	$1,300.15	$1,300.30