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	$88.30	7.865%	$95.2448	$95.24	$95.25	$95.20
Purchase #2	$36.75	4.120%	$38.2641	$38.26	$38.25	$38.30
Purchase #3	$96.75	3.765%	$100.3926	$100.39	$100.40	$100.40
Purchase #4	$101.43	4.279%	$105.7702	$105.77	$105.75	$105.80
Purchase #5	$180.79	3.518%	$187.1502	$187.15	$187.15	$187.20
Purchase #6	$56.96	6.721%	$60.7883	$60.79	$60.80	$60.80
Purchase #7	$63.66	13.540%	$72.2796	$72.28	$72.30	$72.30
7 purchase totals =	$624.64		$659.8898	$659.88	$659.90	$660.00