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	$148.33	9.406%	$162.2819	$162.28	$162.30	$162.30
Purchase #2	$109.44	12.557%	$123.1824	$123.18	$123.20	$123.20
Purchase #3	$121.32	4.711%	$127.0354	$127.04	$127.05	$127.00
Purchase #4	$203.51	3.635%	$210.9076	$210.91	$210.90	$210.90
Purchase #5	$35.35	9.408%	$38.6757	$38.68	$38.70	$38.70
Purchase #6	$19.31	5.708%	$20.4122	$20.41	$20.40	$20.40
Purchase #7	$134.34	5.675%	$141.9638	$141.96	$141.95	$142.00
7 purchase totals =	$771.60		$824.4590	$824.46	$824.50	$824.50