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	$51.86	7.470%	$55.7339	$55.73	$55.75	$55.70
Purchase #2	$145.89	4.374%	$152.2712	$152.27	$152.25	$152.30
Purchase #3	$196.60	7.722%	$211.7815	$211.78	$211.80	$211.80
Purchase #4	$200.37	3.769%	$207.9219	$207.92	$207.90	$207.90
Purchase #5	$224.68	11.378%	$250.2441	$250.24	$250.25	$250.20
Purchase #6	$141.44	6.841%	$151.1159	$151.12	$151.10	$151.10
Purchase #7	$59.66	13.865%	$67.9319	$67.93	$67.95	$67.90
7 purchase totals =	$1,020.50		$1,097.0004	$1,096.99	$1,097.00	$1,096.90