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	$201.86	10.776%	$223.6124	$223.61	$223.60	$223.60
Purchase #2	$120.78	11.309%	$134.439	$134.44	$134.45	$134.40
Purchase #3	$14.46	3.862%	$15.0184	$15.02	$15.00	$15.00
Purchase #4	$232.29	4.424%	$242.5665	$242.57	$242.55	$242.60
Purchase #5	$171.59	11.492%	$191.3091	$191.31	$191.30	$191.30
Purchase #6	$89.69	4.284%	$93.5323	$93.53	$93.55	$93.50
Purchase #7	$187.47	4.223%	$195.3869	$195.39	$195.40	$195.40
7 purchase totals =	$1,018.14		$1,095.8646	$1,095.87	$1,095.85	$1,095.80