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	$118.45	7.813%	$127.7045	$127.70	$127.70	$127.70
Purchase #2	$216.82	8.276%	$234.764	$234.76	$234.75	$234.80
Purchase #3	$215.89	13.854%	$245.7994	$245.80	$245.80	$245.80
Purchase #4	$88.41	10.298%	$97.5145	$97.51	$97.50	$97.50
Purchase #5	$131.92	6.328%	$140.2679	$140.27	$140.25	$140.30
Purchase #6	$164.58	10.109%	$181.2174	$181.22	$181.20	$181.20
Purchase #7	$89.98	11.281%	$100.1306	$100.13	$100.15	$100.10
7 purchase totals =	$1,026.05		$1,127.3983	$1,127.39	$1,127.35	$1,127.40