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	$93.38	12.310%	$104.8751	$104.88	$104.90	$104.90
Purchase #2	$48.80	5.227%	$51.3508	$51.35	$51.35	$51.40
Purchase #3	$123.88	5.278%	$130.4184	$130.42	$130.40	$130.40
Purchase #4	$174.82	12.195%	$196.1393	$196.14	$196.15	$196.10
Purchase #5	$65.84	6.361%	$70.0281	$70.03	$70.05	$70.00
Purchase #6	$89.36	7.770%	$96.3033	$96.30	$96.30	$96.30
Purchase #7	$98.64	11.195%	$109.6827	$109.68	$109.70	$109.70
7 purchase totals =	$694.72		$758.7977	$758.80	$758.85	$758.80