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	$98.42	5.407%	$103.7416	$103.74	$103.75	$103.70
Purchase #2	$109.83	8.249%	$118.8899	$118.89	$118.90	$118.90
Purchase #3	$242.51	11.467%	$270.3186	$270.32	$270.30	$270.30
Purchase #4	$179.31	11.487%	$199.9073	$199.91	$199.90	$199.90
Purchase #5	$160.57	11.638%	$179.2571	$179.26	$179.25	$179.30
Purchase #6	$86.64	5.200%	$91.1453	$91.15	$91.15	$91.10
Purchase #7	$49.66	5.120%	$52.2026	$52.20	$52.20	$52.20
7 purchase totals =	$926.94		$1,015.4624	$1,015.47	$1,015.45	$1,015.40