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	$188.54	4.754%	$197.5032	$197.50	$197.50	$197.50
Purchase #2	$73.29	11.728%	$81.8855	$81.89	$81.90	$81.90
Purchase #3	$29.79	4.446%	$31.1145	$31.11	$31.10	$31.10
Purchase #4	$133.80	13.774%	$152.2296	$152.23	$152.25	$152.20
Purchase #5	$13.55	4.446%	$14.1524	$14.15	$14.15	$14.20
Purchase #6	$191.89	13.137%	$217.0986	$217.10	$217.10	$217.10
Purchase #7	$150.83	10.242%	$166.278	$166.28	$166.30	$166.30
7 purchase totals =	$781.69		$860.2618	$860.26	$860.30	$860.30