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	$162.47	10.144%	$178.951	$178.95	$178.95	$179.00
Purchase #2	$145.73	11.373%	$162.3039	$162.30	$162.30	$162.30
Purchase #3	$42.97	6.476%	$45.7527	$45.75	$45.75	$45.80
Purchase #4	$79.93	3.237%	$82.5173	$82.52	$82.50	$82.50
Purchase #5	$227.27	9.469%	$248.7902	$248.79	$248.80	$248.80
Purchase #6	$45.91	13.745%	$52.2203	$52.22	$52.20	$52.20
Purchase #7	$249.35	5.575%	$263.2513	$263.25	$263.25	$263.30
7 purchase totals =	$953.63		$1,033.7867	$1,033.78	$1,033.75	$1,033.90