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	$188.38	9.837%	$206.9109	$206.91	$206.90	$206.90
Purchase #2	$63.63	11.852%	$71.1714	$71.17	$71.15	$71.20
Purchase #3	$175.78	7.140%	$188.3307	$188.33	$188.35	$188.30
Purchase #4	$154.34	9.565%	$169.1026	$169.10	$169.10	$169.10
Purchase #5	$99.86	13.711%	$113.5518	$113.55	$113.55	$113.60
Purchase #6	$73.88	4.648%	$77.3139	$77.31	$77.30	$77.30
Purchase #7	$73.35	9.196%	$80.0953	$80.10	$80.10	$80.10
7 purchase totals =	$829.22		$906.4766	$906.47	$906.45	$906.50