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	$206.83	5.620%	$218.4538	$218.45	$218.45	$218.50
Purchase #2	$83.82	9.120%	$91.4644	$91.46	$91.45	$91.50
Purchase #3	$209.66	11.557%	$233.8904	$233.89	$233.90	$233.90
Purchase #4	$53.95	11.309%	$60.0512	$60.05	$60.05	$60.10
Purchase #5	$88.31	4.470%	$92.2575	$92.26	$92.25	$92.30
Purchase #6	$171.59	13.331%	$194.4647	$194.46	$194.45	$194.50
Purchase #7	$178.35	4.288%	$185.9976	$186.00	$186.00	$186.00
7 purchase totals =	$992.51		$1,076.5796	$1,076.57	$1,076.55	$1,076.80