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	$169.93	11.670%	$189.7608	$189.76	$189.75	$189.80
Purchase #2	$93.29	8.561%	$101.2766	$101.28	$101.30	$101.30
Purchase #3	$59.28	3.811%	$61.5392	$61.54	$61.55	$61.50
Purchase #4	$118.41	10.852%	$131.2599	$131.26	$131.25	$131.30
Purchase #5	$79.50	13.614%	$90.3231	$90.32	$90.30	$90.30
Purchase #6	$245.34	5.864%	$259.7267	$259.73	$259.75	$259.70
Purchase #7	$208.45	4.376%	$217.5718	$217.57	$217.55	$217.60
7 purchase totals =	$974.20		$1,051.4581	$1,051.46	$1,051.45	$1,051.50