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	$115.81	11.147%	$128.7193	$128.72	$128.70	$128.70
Purchase #2	$118.86	10.459%	$131.2916	$131.29	$131.30	$131.30
Purchase #3	$56.56	10.808%	$62.673	$62.67	$62.65	$62.70
Purchase #4	$38.91	12.399%	$43.7345	$43.73	$43.75	$43.70
Purchase #5	$154.32	12.798%	$174.0699	$174.07	$174.05	$174.10
Purchase #6	$29.48	12.740%	$33.2358	$33.24	$33.25	$33.20
Purchase #7	$177.81	11.790%	$198.7738	$198.77	$198.75	$198.80
7 purchase totals =	$691.75		$772.4979	$772.49	$772.45	$772.50