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	$155.96	13.408%	$176.8711	$176.87	$176.85	$176.90
Purchase #2	$147.69	5.328%	$155.5589	$155.56	$155.55	$155.60
Purchase #3	$35.33	7.321%	$37.9165	$37.92	$37.90	$37.90
Purchase #4	$220.38	11.589%	$245.9198	$245.92	$245.90	$245.90
Purchase #5	$210.83	10.654%	$233.2918	$233.29	$233.30	$233.30
Purchase #6	$59.75	9.143%	$65.2129	$65.21	$65.20	$65.20
Purchase #7	$200.73	10.734%	$222.2764	$222.28	$222.30	$222.30
7 purchase totals =	$1,030.67		$1,137.0474	$1,137.05	$1,137.00	$1,137.10