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	$167.63	10.713%	$185.5882	$185.59	$185.60	$185.60
Purchase #2	$166.25	10.735%	$184.0969	$184.10	$184.10	$184.10
Purchase #3	$83.83	11.641%	$93.5887	$93.59	$93.60	$93.60
Purchase #4	$201.60	10.679%	$223.1289	$223.13	$223.15	$223.10
Purchase #5	$80.49	11.730%	$89.9315	$89.93	$89.95	$89.90
Purchase #6	$66.70	6.267%	$70.8801	$70.88	$70.90	$70.90
Purchase #7	$154.46	12.648%	$173.9961	$174.00	$174.00	$174.00
7 purchase totals =	$920.96		$1,021.2104	$1,021.22	$1,021.30	$1,021.20