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	$141.70	8.358%	$153.5433	$153.54	$153.55	$153.50
Purchase #2	$46.72	9.723%	$51.2626	$51.26	$51.25	$51.30
Purchase #3	$96.76	9.833%	$106.2744	$106.27	$106.25	$106.30
Purchase #4	$107.73	6.787%	$115.0416	$115.04	$115.05	$115.00
Purchase #5	$94.43	6.242%	$100.3243	$100.32	$100.30	$100.30
Purchase #6	$164.98	12.609%	$185.7823	$185.78	$185.80	$185.80
Purchase #7	$165.32	5.440%	$174.3134	$174.31	$174.30	$174.30
7 purchase totals =	$817.64		$886.5419	$886.52	$886.50	$886.50