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	$204.29	9.677%	$224.0591	$224.06	$224.05	$224.10
Purchase #2	$128.73	10.503%	$142.2505	$142.25	$142.25	$142.30
Purchase #3	$59.63	9.215%	$65.1249	$65.12	$65.10	$65.10
Purchase #4	$182.33	3.869%	$189.3843	$189.38	$189.40	$189.40
Purchase #5	$170.92	8.284%	$185.079	$185.08	$185.10	$185.10
Purchase #6	$112.57	10.289%	$124.1523	$124.15	$124.15	$124.20
Purchase #7	$41.90	10.394%	$46.2551	$46.26	$46.25	$46.30
7 purchase totals =	$900.37		$976.3052	$976.30	$976.30	$976.50