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	$174.40	7.370%	$187.2533	$187.25	$187.25	$187.30
Purchase #2	$20.74	13.808%	$23.6038	$23.60	$23.60	$23.60
Purchase #3	$148.69	11.790%	$166.2206	$166.22	$166.20	$166.20
Purchase #4	$100.48	9.392%	$109.9171	$109.92	$109.90	$109.90
Purchase #5	$250.47	13.859%	$285.1826	$285.18	$285.20	$285.20
Purchase #6	$179.27	8.346%	$194.2319	$194.23	$194.25	$194.20
Purchase #7	$50.43	4.831%	$52.8663	$52.87	$52.85	$52.90
7 purchase totals =	$924.48		$1,019.2756	$1,019.27	$1,019.25	$1,019.30