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	$78.75	4.720%	$82.467	$82.47	$82.45	$82.50
Purchase #2	$246.65	4.165%	$256.923	$256.92	$256.90	$256.90
Purchase #3	$199.44	11.279%	$221.9348	$221.93	$221.95	$221.90
Purchase #4	$150.28	3.707%	$155.8509	$155.85	$155.85	$155.90
Purchase #5	$175.38	6.209%	$186.2693	$186.27	$186.25	$186.30
Purchase #6	$63.61	5.871%	$67.3445	$67.34	$67.35	$67.30
Purchase #7	$176.80	13.306%	$200.325	$200.33	$200.35	$200.30
7 purchase totals =	$1,090.91		$1,171.1145	$1,171.11	$1,171.10	$1,171.10