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	$174.77	6.716%	$186.5076	$186.51	$186.50	$186.50
Purchase #2	$64.92	4.601%	$67.907	$67.91	$67.90	$67.90
Purchase #3	$154.50	10.397%	$170.5634	$170.56	$170.55	$170.60
Purchase #4	$107.73	7.723%	$116.05	$116.05	$116.05	$116.10
Purchase #5	$100.44	3.495%	$103.9504	$103.95	$103.95	$104.00
Purchase #6	$234.74	4.377%	$245.0146	$245.01	$245.00	$245.00
Purchase #7	$183.48	4.330%	$191.4247	$191.42	$191.40	$191.40
7 purchase totals =	$1,020.58		$1,081.4177	$1,081.41	$1,081.35	$1,081.50