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	$122.60	3.829%	$127.2944	$127.29	$127.30	$127.30
Purchase #2	$166.97	9.761%	$183.2679	$183.27	$183.25	$183.30
Purchase #3	$153.35	10.290%	$169.1297	$169.13	$169.15	$169.10
Purchase #4	$56.31	12.361%	$63.2705	$63.27	$63.25	$63.30
Purchase #5	$158.31	6.358%	$168.3753	$168.38	$168.40	$168.40
Purchase #6	$92.52	7.561%	$99.5154	$99.52	$99.50	$99.50
Purchase #7	$237.33	3.460%	$245.5416	$245.54	$245.55	$245.50
7 purchase totals =	$987.39		$1,056.3948	$1,056.40	$1,056.40	$1,056.40