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	$206.41	3.139%	$212.8892	$212.89	$212.90	$212.90
Purchase #2	$87.92	12.867%	$99.2327	$99.23	$99.25	$99.20
Purchase #3	$240.78	4.585%	$251.8198	$251.82	$251.80	$251.80
Purchase #4	$145.52	4.411%	$151.9389	$151.94	$151.95	$151.90
Purchase #5	$181.53	11.771%	$202.8979	$202.90	$202.90	$202.90
Purchase #6	$86.80	3.633%	$89.9534	$89.95	$89.95	$90.00
Purchase #7	$179.56	11.541%	$200.283	$200.28	$200.30	$200.30
7 purchase totals =	$1,128.52		$1,209.0149	$1,209.01	$1,209.05	$1,209.00