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	$127.74	4.302%	$133.2354	$133.24	$133.25	$133.20
Purchase #2	$73.46	3.475%	$76.0127	$76.01	$76.00	$76.00
Purchase #3	$149.85	4.281%	$156.2651	$156.27	$156.25	$156.30
Purchase #4	$114.27	6.379%	$121.5593	$121.56	$121.55	$121.60
Purchase #5	$141.39	10.553%	$156.3109	$156.31	$156.30	$156.30
Purchase #6	$185.79	3.132%	$191.6089	$191.61	$191.60	$191.60
Purchase #7	$93.84	4.738%	$98.2861	$98.29	$98.30	$98.30
7 purchase totals =	$886.34		$933.2784	$933.29	$933.25	$933.30