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	$68.50	12.435%	$77.018	$77.02	$77.00	$77.00
Purchase #2	$89.61	6.784%	$95.6891	$95.69	$95.70	$95.70
Purchase #3	$176.38	10.277%	$194.5066	$194.51	$194.50	$194.50
Purchase #4	$169.25	11.466%	$188.6562	$188.66	$188.65	$188.70
Purchase #5	$167.55	6.868%	$179.0573	$179.06	$179.05	$179.10
Purchase #6	$156.62	6.530%	$166.8473	$166.85	$166.85	$166.80
Purchase #7	$96.47	11.474%	$107.539	$107.54	$107.55	$107.50
7 purchase totals =	$924.38		$1,009.3135	$1,009.33	$1,009.30	$1,009.30