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	$50.64	8.850%	$55.1216	$55.12	$55.10	$55.10
Purchase #2	$64.34	6.231%	$68.349	$68.35	$68.35	$68.30
Purchase #3	$191.56	8.740%	$208.3023	$208.30	$208.30	$208.30
Purchase #4	$181.94	4.651%	$190.402	$190.40	$190.40	$190.40
Purchase #5	$85.46	8.701%	$92.8959	$92.90	$92.90	$92.90
Purchase #6	$127.74	13.714%	$145.2583	$145.26	$145.25	$145.30
Purchase #7	$12.74	4.505%	$13.3139	$13.31	$13.30	$13.30
7 purchase totals =	$714.42		$773.6430	$773.64	$773.60	$773.60