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	$150.59	13.512%	$170.9377	$170.94	$170.95	$170.90
Purchase #2	$213.80	13.805%	$243.3151	$243.32	$243.30	$243.30
Purchase #3	$7.28	4.107%	$7.579	$7.58	$7.60	$7.60
Purchase #4	$145.41	13.303%	$164.7539	$164.75	$164.75	$164.80
Purchase #5	$168.83	5.591%	$178.2693	$178.27	$178.25	$178.30
Purchase #6	$56.55	9.607%	$61.9828	$61.98	$62.00	$62.00
Purchase #7	$167.91	9.365%	$183.6348	$183.63	$183.65	$183.60
7 purchase totals =	$910.37		$1,010.4726	$1,010.47	$1,010.50	$1,010.50