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	$158.53	12.738%	$178.7236	$178.72	$178.70	$178.70
Purchase #2	$18.92	11.797%	$21.152	$21.15	$21.15	$21.20
Purchase #3	$104.56	4.285%	$109.0404	$109.04	$109.05	$109.00
Purchase #4	$211.48	10.781%	$234.2797	$234.28	$234.30	$234.30
Purchase #5	$215.74	12.662%	$243.057	$243.06	$243.05	$243.10
Purchase #6	$240.71	3.274%	$248.5908	$248.59	$248.60	$248.60
Purchase #7	$11.33	9.785%	$12.4386	$12.44	$12.45	$12.40
7 purchase totals =	$961.27		$1,047.2821	$1,047.28	$1,047.30	$1,047.30