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	$25.53	12.112%	$28.6222	$28.62	$28.60	$28.60
Purchase #2	$248.76	4.134%	$259.0437	$259.04	$259.05	$259.00
Purchase #3	$13.63	5.784%	$14.4184	$14.42	$14.40	$14.40
Purchase #4	$78.76	6.260%	$83.6904	$83.69	$83.70	$83.70
Purchase #5	$104.90	4.301%	$109.4117	$109.41	$109.40	$109.40
Purchase #6	$136.43	4.487%	$142.5516	$142.55	$142.55	$142.60
Purchase #7	$84.67	13.498%	$96.0988	$96.10	$96.10	$96.10
7 purchase totals =	$692.68		$733.8368	$733.83	$733.80	$733.80