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	$163.59	3.505%	$169.3238	$169.32	$169.30	$169.30
Purchase #2	$93.27	5.510%	$98.4092	$98.41	$98.40	$98.40
Purchase #3	$187.26	12.616%	$210.8847	$210.88	$210.90	$210.90
Purchase #4	$234.89	4.345%	$245.096	$245.10	$245.10	$245.10
Purchase #5	$116.68	5.562%	$123.1697	$123.17	$123.15	$123.20
Purchase #6	$72.78	11.710%	$81.3025	$81.30	$81.30	$81.30
Purchase #7	$151.25	13.633%	$171.8699	$171.87	$171.85	$171.90
7 purchase totals =	$1,019.72		$1,100.0558	$1,100.05	$1,100.00	$1,100.10