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	$235.94	11.820%	$263.8281	$263.83	$263.85	$263.80
Purchase #2	$68.37	6.495%	$72.8106	$72.81	$72.80	$72.80
Purchase #3	$23.41	8.312%	$25.3558	$25.36	$25.35	$25.40
Purchase #4	$70.49	8.519%	$76.495	$76.50	$76.50	$76.50
Purchase #5	$79.50	8.488%	$86.248	$86.25	$86.25	$86.20
Purchase #6	$82.62	8.782%	$89.8757	$89.88	$89.90	$89.90
Purchase #7	$146.85	13.710%	$166.9831	$166.98	$167.00	$167.00
7 purchase totals =	$707.18		$781.5963	$781.61	$781.65	$781.60