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	$212.60	4.870%	$222.9536	$222.95	$222.95	$223.00
Purchase #2	$174.77	3.857%	$181.5109	$181.51	$181.50	$181.50
Purchase #3	$42.29	9.497%	$46.3063	$46.31	$46.30	$46.30
Purchase #4	$86.87	10.660%	$96.1303	$96.13	$96.15	$96.10
Purchase #5	$23.64	6.761%	$25.2383	$25.24	$25.25	$25.20
Purchase #6	$134.81	9.246%	$147.2745	$147.27	$147.25	$147.30
Purchase #7	$205.41	3.165%	$211.9112	$211.91	$211.90	$211.90
7 purchase totals =	$880.39		$931.3251	$931.32	$931.30	$931.30