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	$41.47	4.543%	$43.354	$43.35	$43.35	$43.40
Purchase #2	$39.35	4.775%	$41.229	$41.23	$41.25	$41.20
Purchase #3	$53.48	3.465%	$55.3331	$55.33	$55.35	$55.30
Purchase #4	$170.83	10.190%	$188.2376	$188.24	$188.25	$188.20
Purchase #5	$9.54	13.587%	$10.8362	$10.84	$10.85	$10.80
Purchase #6	$56.83	4.842%	$59.5817	$59.58	$59.60	$59.60
Purchase #7	$16.42	3.673%	$17.0231	$17.02	$17.00	$17.00
7 purchase totals =	$387.92		$415.5947	$415.59	$415.65	$415.50