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	$120.91	5.148%	$127.1344	$127.13	$127.15	$127.10
Purchase #2	$213.44	4.116%	$222.2252	$222.23	$222.25	$222.20
Purchase #3	$215.76	9.417%	$236.0781	$236.08	$236.10	$236.10
Purchase #4	$113.36	13.282%	$128.4165	$128.42	$128.40	$128.40
Purchase #5	$29.74	13.617%	$33.7897	$33.79	$33.80	$33.80
Purchase #6	$81.29	7.681%	$87.5339	$87.53	$87.55	$87.50
Purchase #7	$234.28	9.304%	$256.0774	$256.08	$256.10	$256.10
7 purchase totals =	$1,008.78		$1,091.2552	$1,091.26	$1,091.35	$1,091.20