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	$141.92	12.483%	$159.6359	$159.64	$159.65	$159.60
Purchase #2	$86.90	6.810%	$92.8179	$92.82	$92.80	$92.80
Purchase #3	$19.45	9.784%	$21.353	$21.35	$21.35	$21.40
Purchase #4	$244.73	4.416%	$255.5373	$255.54	$255.55	$255.50
Purchase #5	$25.98	5.198%	$27.3304	$27.33	$27.35	$27.30
Purchase #6	$215.63	12.475%	$242.5298	$242.53	$242.55	$242.50
Purchase #7	$197.28	9.300%	$215.627	$215.63	$215.65	$215.60
7 purchase totals =	$931.89		$1,014.8313	$1,014.84	$1,014.90	$1,014.70