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	$69.46	11.493%	$77.443	$77.44	$77.45	$77.40
Purchase #2	$28.61	3.438%	$29.5936	$29.59	$29.60	$29.60
Purchase #3	$122.88	3.839%	$127.5974	$127.60	$127.60	$127.60
Purchase #4	$81.72	9.621%	$89.5823	$89.58	$89.60	$89.60
Purchase #5	$210.32	10.505%	$232.4141	$232.41	$232.40	$232.40
Purchase #6	$54.74	9.865%	$60.1401	$60.14	$60.15	$60.10
Purchase #7	$156.67	7.372%	$168.2197	$168.22	$168.20	$168.20
7 purchase totals =	$724.40		$784.9902	$784.98	$785.00	$784.90