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	$110.66	11.480%	$123.3638	$123.36	$123.35	$123.40
Purchase #2	$8.41	8.402%	$9.1166	$9.12	$9.10	$9.10
Purchase #3	$194.25	11.287%	$216.175	$216.18	$216.20	$216.20
Purchase #4	$98.25	5.216%	$103.3747	$103.37	$103.35	$103.40
Purchase #5	$117.95	11.817%	$131.8882	$131.89	$131.90	$131.90
Purchase #6	$236.56	11.838%	$264.564	$264.56	$264.55	$264.60
Purchase #7	$53.66	3.336%	$55.4501	$55.45	$55.45	$55.50
7 purchase totals =	$819.74		$903.9324	$903.93	$903.90	$904.10