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	$98.82	13.591%	$112.2506	$112.25	$112.25	$112.30
Purchase #2	$158.33	5.626%	$167.2376	$167.24	$167.25	$167.20
Purchase #3	$89.29	4.403%	$93.2214	$93.22	$93.20	$93.20
Purchase #4	$12.26	9.152%	$13.382	$13.38	$13.40	$13.40
Purchase #5	$249.80	7.852%	$269.4143	$269.41	$269.40	$269.40
Purchase #6	$115.82	13.746%	$131.7406	$131.74	$131.75	$131.70
Purchase #7	$83.76	6.418%	$89.1357	$89.14	$89.15	$89.10
7 purchase totals =	$808.08		$876.3822	$876.38	$876.40	$876.30