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	$96.28	5.192%	$101.2789	$101.28	$101.30	$101.30
Purchase #2	$204.44	5.647%	$215.9847	$215.98	$216.00	$216.00
Purchase #3	$120.36	11.705%	$134.4481	$134.45	$134.45	$134.40
Purchase #4	$76.27	5.651%	$80.58	$80.58	$80.60	$80.60
Purchase #5	$148.60	11.244%	$165.3086	$165.31	$165.30	$165.30
Purchase #6	$173.81	4.683%	$181.9495	$181.95	$181.95	$181.90
Purchase #7	$190.96	10.403%	$210.8256	$210.83	$210.85	$210.80
7 purchase totals =	$1,010.72		$1,090.3754	$1,090.38	$1,090.45	$1,090.30