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	$142.84	7.636%	$153.7473	$153.75	$153.75	$153.70
Purchase #2	$79.30	5.702%	$83.8217	$83.82	$83.80	$83.80
Purchase #3	$101.56	7.421%	$109.0968	$109.10	$109.10	$109.10
Purchase #4	$223.79	6.201%	$237.6672	$237.67	$237.65	$237.70
Purchase #5	$41.72	3.801%	$43.3058	$43.31	$43.30	$43.30
Purchase #6	$95.52	10.290%	$105.349	$105.35	$105.35	$105.30
Purchase #7	$235.61	7.735%	$253.8344	$253.83	$253.85	$253.80
7 purchase totals =	$920.34		$986.8222	$986.83	$986.80	$986.70