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	$162.29	7.464%	$174.4033	$174.40	$174.40	$174.40
Purchase #2	$87.98	5.459%	$92.7828	$92.78	$92.80	$92.80
Purchase #3	$58.89	9.477%	$64.471	$64.47	$64.45	$64.50
Purchase #4	$58.83	4.156%	$61.275	$61.28	$61.30	$61.30
Purchase #5	$47.77	3.126%	$49.2633	$49.26	$49.25	$49.30
Purchase #6	$92.50	13.294%	$104.797	$104.80	$104.80	$104.80
Purchase #7	$228.52	7.607%	$245.9035	$245.90	$245.90	$245.90
7 purchase totals =	$736.78		$792.8959	$792.89	$792.90	$793.00