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	$178.59	5.407%	$188.2464	$188.25	$188.25	$188.20
Purchase #2	$187.78	12.789%	$211.7952	$211.80	$211.80	$211.80
Purchase #3	$59.58	5.280%	$62.7258	$62.73	$62.75	$62.70
Purchase #4	$233.26	10.760%	$258.3588	$258.36	$258.35	$258.40
Purchase #5	$128.81	5.795%	$136.2745	$136.27	$136.25	$136.30
Purchase #6	$50.88	4.648%	$53.2449	$53.24	$53.25	$53.20
Purchase #7	$166.36	11.578%	$185.6212	$185.62	$185.60	$185.60
7 purchase totals =	$1,005.26		$1,096.2668	$1,096.27	$1,096.25	$1,096.20