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	$72.46	8.873%	$78.8894	$78.89	$78.90	$78.90
Purchase #2	$51.32	11.568%	$57.2567	$57.26	$57.25	$57.30
Purchase #3	$181.75	9.347%	$198.7382	$198.74	$198.75	$198.70
Purchase #4	$226.80	6.607%	$241.7847	$241.78	$241.80	$241.80
Purchase #5	$151.25	13.637%	$171.876	$171.88	$171.90	$171.90
Purchase #6	$114.41	12.403%	$128.6003	$128.60	$128.60	$128.60
Purchase #7	$210.49	11.234%	$234.1364	$234.14	$234.15	$234.10
7 purchase totals =	$1,008.48		$1,111.2817	$1,111.29	$1,111.35	$1,111.30