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	$63.37	7.425%	$68.0752	$68.08	$68.10	$68.10
Purchase #2	$90.56	4.567%	$94.6959	$94.70	$94.70	$94.70
Purchase #3	$171.69	6.214%	$182.3588	$182.36	$182.35	$182.40
Purchase #4	$84.84	6.577%	$90.4199	$90.42	$90.40	$90.40
Purchase #5	$88.71	12.158%	$99.4954	$99.50	$99.50	$99.50
Purchase #6	$190.77	9.720%	$209.3128	$209.31	$209.30	$209.30
Purchase #7	$37.44	10.333%	$41.3087	$41.31	$41.30	$41.30
7 purchase totals =	$727.38		$785.6667	$785.68	$785.65	$785.70