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	$179.94	3.455%	$186.1569	$186.16	$186.15	$186.20
Purchase #2	$209.33	12.333%	$235.1467	$235.15	$235.15	$235.10
Purchase #3	$93.46	4.646%	$97.8022	$97.80	$97.80	$97.80
Purchase #4	$13.85	6.328%	$14.7264	$14.73	$14.75	$14.70
Purchase #5	$91.82	9.707%	$100.733	$100.73	$100.75	$100.70
Purchase #6	$243.67	10.219%	$268.5706	$268.57	$268.55	$268.60
Purchase #7	$109.95	3.524%	$113.8246	$113.82	$113.80	$113.80
7 purchase totals =	$942.02		$1,016.9604	$1,016.96	$1,016.95	$1,016.90