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	$162.87	9.335%	$178.0739	$178.07	$178.05	$178.10
Purchase #2	$103.99	7.808%	$112.1095	$112.11	$112.10	$112.10
Purchase #3	$162.91	13.701%	$185.2303	$185.23	$185.25	$185.20
Purchase #4	$49.57	5.418%	$52.2557	$52.26	$52.25	$52.30
Purchase #5	$147.49	4.740%	$154.481	$154.48	$154.50	$154.50
Purchase #6	$33.25	12.799%	$37.5057	$37.51	$37.50	$37.50
Purchase #7	$57.46	8.358%	$62.2625	$62.26	$62.25	$62.30
7 purchase totals =	$717.54		$781.9186	$781.92	$781.90	$782.00