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	$191.56	9.642%	$210.0302	$210.03	$210.05	$210.00
Purchase #2	$167.41	11.357%	$186.4228	$186.42	$186.40	$186.40
Purchase #3	$68.97	5.707%	$72.9061	$72.91	$72.90	$72.90
Purchase #4	$217.36	5.564%	$229.4539	$229.45	$229.45	$229.50
Purchase #5	$83.46	7.282%	$89.5376	$89.54	$89.55	$89.50
Purchase #6	$71.72	8.312%	$77.6814	$77.68	$77.70	$77.70
Purchase #7	$110.66	4.302%	$115.4206	$115.42	$115.40	$115.40
7 purchase totals =	$911.14		$981.4526	$981.45	$981.45	$981.40