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	$218.31	11.421%	$243.2432	$243.24	$243.25	$243.20
Purchase #2	$167.65	12.654%	$188.8644	$188.86	$188.85	$188.90
Purchase #3	$146.39	4.212%	$152.5559	$152.56	$152.55	$152.60
Purchase #4	$141.33	6.554%	$150.5928	$150.59	$150.60	$150.60
Purchase #5	$246.66	9.426%	$269.9102	$269.91	$269.90	$269.90
Purchase #6	$163.95	6.279%	$174.2444	$174.24	$174.25	$174.20
Purchase #7	$75.40	13.234%	$85.3784	$85.38	$85.40	$85.40
7 purchase totals =	$1,159.69		$1,264.7893	$1,264.78	$1,264.80	$1,264.80