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	$153.32	4.415%	$160.0891	$160.09	$160.10	$160.10
Purchase #2	$129.48	7.483%	$139.169	$139.17	$139.15	$139.20
Purchase #3	$233.38	3.231%	$240.9205	$240.92	$240.90	$240.90
Purchase #4	$115.32	10.696%	$127.6546	$127.65	$127.65	$127.70
Purchase #5	$54.60	3.106%	$56.2959	$56.30	$56.30	$56.30
Purchase #6	$127.97	8.859%	$139.3069	$139.31	$139.30	$139.30
Purchase #7	$98.54	11.422%	$109.7952	$109.80	$109.80	$109.80
7 purchase totals =	$912.61		$973.2312	$973.24	$973.20	$973.30