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	$109.32	7.857%	$117.9093	$117.91	$117.90	$117.90
Purchase #2	$55.93	6.107%	$59.3456	$59.35	$59.35	$59.30
Purchase #3	$180.72	6.240%	$191.9969	$192.00	$192.00	$192.00
Purchase #4	$240.37	11.615%	$268.289	$268.29	$268.30	$268.30
Purchase #5	$120.28	4.333%	$125.4917	$125.49	$125.50	$125.50
Purchase #6	$117.52	9.821%	$129.0616	$129.06	$129.05	$129.10
Purchase #7	$247.37	13.518%	$280.8095	$280.81	$280.80	$280.80
7 purchase totals =	$1,071.51		$1,172.9036	$1,172.91	$1,172.90	$1,172.90