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	$56.32	5.168%	$59.2306	$59.23	$59.25	$59.20
Purchase #2	$227.70	13.631%	$258.7378	$258.74	$258.75	$258.70
Purchase #3	$189.65	11.112%	$210.7239	$210.72	$210.70	$210.70
Purchase #4	$191.85	12.247%	$215.3459	$215.35	$215.35	$215.30
Purchase #5	$186.72	13.216%	$211.3969	$211.40	$211.40	$211.40
Purchase #6	$71.35	7.149%	$76.4508	$76.45	$76.45	$76.50
Purchase #7	$238.92	11.663%	$266.7852	$266.79	$266.80	$266.80
7 purchase totals =	$1,162.51		$1,298.6711	$1,298.68	$1,298.70	$1,298.60