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	$100.90	4.391%	$105.3305	$105.33	$105.35	$105.30
Purchase #2	$167.99	6.681%	$179.2134	$179.21	$179.20	$179.20
Purchase #3	$211.85	10.352%	$233.7807	$233.78	$233.80	$233.80
Purchase #4	$104.73	9.721%	$114.9108	$114.91	$114.90	$114.90
Purchase #5	$228.28	8.756%	$248.2682	$248.27	$248.25	$248.30
Purchase #6	$43.90	7.697%	$47.279	$47.28	$47.30	$47.30
Purchase #7	$196.73	11.475%	$219.3048	$219.30	$219.30	$219.30
7 purchase totals =	$1,054.38		$1,148.0874	$1,148.08	$1,148.10	$1,148.10