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	$127.58	7.692%	$137.3935	$137.39	$137.40	$137.40
Purchase #2	$30.88	6.300%	$32.8254	$32.83	$32.85	$32.80
Purchase #3	$206.84	10.737%	$229.0484	$229.05	$229.05	$229.00
Purchase #4	$82.39	12.212%	$92.4515	$92.45	$92.45	$92.50
Purchase #5	$144.97	5.727%	$153.2724	$153.27	$153.25	$153.30
Purchase #6	$220.96	13.271%	$250.2836	$250.28	$250.30	$250.30
Purchase #7	$72.83	5.794%	$77.0498	$77.05	$77.05	$77.00
7 purchase totals =	$886.45		$972.3246	$972.32	$972.35	$972.30