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	$68.76	13.814%	$78.2585	$78.26	$78.25	$78.30
Purchase #2	$111.73	7.544%	$120.1589	$120.16	$120.15	$120.20
Purchase #3	$42.49	8.848%	$46.2495	$46.25	$46.25	$46.20
Purchase #4	$100.50	4.872%	$105.3964	$105.40	$105.40	$105.40
Purchase #5	$145.36	11.824%	$162.5474	$162.55	$162.55	$162.50
Purchase #6	$211.41	12.376%	$237.5741	$237.57	$237.55	$237.60
Purchase #7	$100.66	13.839%	$114.5903	$114.59	$114.60	$114.60
7 purchase totals =	$780.91		$864.7751	$864.78	$864.75	$864.80