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	$91.40	9.184%	$99.7942	$99.79	$99.80	$99.80
Purchase #2	$232.47	3.816%	$241.3411	$241.34	$241.35	$241.30
Purchase #3	$201.96	8.357%	$218.8378	$218.84	$218.85	$218.80
Purchase #4	$72.87	13.111%	$82.424	$82.42	$82.40	$82.40
Purchase #5	$198.36	12.538%	$223.2304	$223.23	$223.25	$223.20
Purchase #6	$149.33	4.396%	$155.8945	$155.89	$155.90	$155.90
Purchase #7	$41.65	13.637%	$47.3298	$47.33	$47.35	$47.30
7 purchase totals =	$988.04		$1,068.8518	$1,068.84	$1,068.90	$1,068.70