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	$173.86	7.498%	$186.896	$186.90	$186.90	$186.90
Purchase #2	$18.72	13.865%	$21.3155	$21.32	$21.30	$21.30
Purchase #3	$162.44	5.811%	$171.8794	$171.88	$171.90	$171.90
Purchase #4	$172.26	11.263%	$191.6616	$191.66	$191.65	$191.70
Purchase #5	$49.61	11.116%	$55.1246	$55.12	$55.10	$55.10
Purchase #6	$139.32	11.396%	$155.1969	$155.20	$155.20	$155.20
Purchase #7	$61.83	4.512%	$64.6198	$64.62	$64.60	$64.60
7 purchase totals =	$778.04		$846.6938	$846.70	$846.65	$846.70