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	$94.92	4.548%	$99.237	$99.24	$99.25	$99.20
Purchase #2	$184.86	6.196%	$196.3139	$196.31	$196.30	$196.30
Purchase #3	$86.64	5.210%	$91.1539	$91.15	$91.15	$91.20
Purchase #4	$72.54	7.306%	$77.8398	$77.84	$77.85	$77.80
Purchase #5	$204.59	12.250%	$229.6523	$229.65	$229.65	$229.70
Purchase #6	$205.86	7.369%	$221.0298	$221.03	$221.05	$221.00
Purchase #7	$157.82	3.123%	$162.7487	$162.75	$162.75	$162.70
7 purchase totals =	$1,007.23		$1,077.9754	$1,077.97	$1,078.00	$1,077.90