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	$31.63	5.586%	$33.3969	$33.40	$33.40	$33.40
Purchase #2	$87.92	9.755%	$96.4966	$96.50	$96.50	$96.50
Purchase #3	$169.72	7.396%	$182.2725	$182.27	$182.25	$182.30
Purchase #4	$202.39	3.572%	$209.6194	$209.62	$209.60	$209.60
Purchase #5	$67.59	6.786%	$72.1767	$72.18	$72.20	$72.20
Purchase #6	$59.82	12.289%	$67.1713	$67.17	$67.15	$67.20
Purchase #7	$191.41	6.823%	$204.4699	$204.47	$204.45	$204.50
7 purchase totals =	$810.48		$865.6033	$865.61	$865.55	$865.70