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	$113.95	3.711%	$118.1787	$118.18	$118.20	$118.20
Purchase #2	$245.92	10.212%	$271.0334	$271.03	$271.05	$271.00
Purchase #3	$191.41	12.404%	$215.1525	$215.15	$215.15	$215.20
Purchase #4	$209.44	4.222%	$218.2826	$218.28	$218.30	$218.30
Purchase #5	$247.55	9.686%	$271.5277	$271.53	$271.55	$271.50
Purchase #6	$52.73	5.151%	$55.4461	$55.45	$55.45	$55.40
Purchase #7	$73.46	6.241%	$78.0446	$78.04	$78.05	$78.00
7 purchase totals =	$1,134.46		$1,227.6656	$1,227.66	$1,227.75	$1,227.60