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	$28.56	13.200%	$32.3299	$32.33	$32.35	$32.30
Purchase #2	$169.93	9.734%	$186.471	$186.47	$186.45	$186.50
Purchase #3	$166.54	11.435%	$185.5838	$185.58	$185.60	$185.60
Purchase #4	$228.76	8.578%	$248.383	$248.38	$248.40	$248.40
Purchase #5	$134.59	3.364%	$139.1176	$139.12	$139.10	$139.10
Purchase #6	$221.52	6.440%	$235.7859	$235.79	$235.80	$235.80
Purchase #7	$76.46	13.221%	$86.5688	$86.57	$86.55	$86.60
7 purchase totals =	$1,026.36		$1,114.2400	$1,114.24	$1,114.25	$1,114.30