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	$41.28	8.464%	$44.7739	$44.77	$44.75	$44.80
Purchase #2	$98.37	11.315%	$109.5006	$109.50	$109.50	$109.50
Purchase #3	$161.36	6.523%	$171.8855	$171.89	$171.90	$171.90
Purchase #4	$109.58	4.782%	$114.8201	$114.82	$114.80	$114.80
Purchase #5	$75.75	3.155%	$78.1399	$78.14	$78.15	$78.10
Purchase #6	$26.66	3.133%	$27.4953	$27.50	$27.50	$27.50
Purchase #7	$123.98	4.468%	$129.5194	$129.52	$129.50	$129.50
7 purchase totals =	$636.98		$676.1347	$676.14	$676.10	$676.10