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	$64.73	11.243%	$72.0076	$72.01	$72.00	$72.00
Purchase #2	$101.78	7.308%	$109.2181	$109.22	$109.20	$109.20
Purchase #3	$64.89	7.698%	$69.8852	$69.89	$69.90	$69.90
Purchase #4	$143.27	7.667%	$154.2545	$154.25	$154.25	$154.30
Purchase #5	$245.40	7.372%	$263.4909	$263.49	$263.50	$263.50
Purchase #6	$234.40	3.408%	$242.3884	$242.39	$242.40	$242.40
Purchase #7	$191.81	9.104%	$209.2724	$209.27	$209.25	$209.30
7 purchase totals =	$1,046.28		$1,120.5171	$1,120.52	$1,120.50	$1,120.60