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	$231.93	9.629%	$254.2625	$254.26	$254.25	$254.30
Purchase #2	$136.27	4.429%	$142.3054	$142.31	$142.30	$142.30
Purchase #3	$180.74	8.557%	$196.2059	$196.21	$196.20	$196.20
Purchase #4	$86.48	12.656%	$97.4249	$97.42	$97.40	$97.40
Purchase #5	$101.62	7.524%	$109.2659	$109.27	$109.25	$109.30
Purchase #6	$127.79	13.670%	$145.2589	$145.26	$145.25	$145.30
Purchase #7	$158.28	5.300%	$166.6688	$166.67	$166.65	$166.70
7 purchase totals =	$1,023.11		$1,111.3923	$1,111.40	$1,111.30	$1,111.50