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	$79.44	12.722%	$89.5464	$89.55	$89.55	$89.50
Purchase #2	$82.80	13.524%	$93.9979	$94.00	$94.00	$94.00
Purchase #3	$20.58	6.117%	$21.8389	$21.84	$21.85	$21.80
Purchase #4	$20.54	8.862%	$22.3603	$22.36	$22.35	$22.40
Purchase #5	$115.61	9.730%	$126.8589	$126.86	$126.85	$126.90
Purchase #6	$125.32	11.136%	$139.2756	$139.28	$139.30	$139.30
Purchase #7	$42.91	11.611%	$47.8923	$47.89	$47.90	$47.90
7 purchase totals =	$487.20		$541.7703	$541.78	$541.80	$541.80